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<title>Database normalization</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Database normalization</span></span>

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<p><b>Database normalization</b> is the process of structuring a <a href="Relational_database" title="Relational database">relational database</a> in accordance with a series of so-called <i><b><a href="#Normal_forms">normal forms</a></b></i> in order to reduce <a href="Data_redundancy" title="Data redundancy">data redundancy</a> and improve <a href="Data_integrity" title="Data integrity">data integrity</a>. It was first proposed by <a href="British_people" title="British people">British</a> <a href="Computer_scientist" title="Computer scientist">computer scientist</a> <a href="Edgar_F._Codd" title="Edgar F. Codd">Edgar F. Codd</a> as part of his <a href="Relational_model" title="Relational model">relational model</a>.

</p><p>Normalization entails organizing the <a href="Column_(database)" title="Column (database)">columns</a> (attributes) and <a href="Relation_(database)" title="Relation (database)">tables</a> (relations) of a database to ensure that their <a href="Dependency_theory_(database_theory)" title="Dependency theory (database theory)">dependencies</a> are properly enforced by database integrity constraints. It is accomplished by applying some formal rules either by a process of <i>synthesis</i> (creating a new database design) or <i>decomposition</i> (improving an existing database design).

</p>

<div class="mw-heading mw-heading2"><h2 id="Objectives">Objectives</h2></div>

<p>A basic objective of the first normal form defined by Codd in 1970 was to permit data to be queried and manipulated using a "universal data sub-language" grounded in <a href="First-order_logic" title="First-order logic">first-order logic</a>.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> An example of such a language is <a href="SQL" title="SQL">SQL</a>, though it is one that Codd regarded as seriously flawed.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p><p>The objectives of normalization beyond 1NF (first normal form) were stated by Codd as:

</p>

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<ol><li>To free the collection of relations from undesirable insertion, update and deletion dependencies.</li>

<li>To reduce the need for restructuring the collection of relations, as new types of data are introduced, and thus increase the life span of application programs.</li>

<li>To make the relational model more informative to users.</li>

<li>To make the collection of relations neutral to the query statistics, where these statistics are liable to change as time goes by.</li></ol>

</blockquote><div class="templatequotecite"><p style="display: inline; padding-left: 2.3em;">— E.F. Codd, "Further Normalisation of the Data Base Relational Model"<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></p></div>

<p>When an attempt is made to modify (update, insert into, or delete from) a relation, the following undesirable side effects may arise in relations that have not been sufficiently normalized:

</p>

<dl><dt>Insertion anomaly</dt>

<dd>There are circumstances in which certain facts cannot be recorded at all. For example, each record in a "Faculty and Their Courses" relation might contain a Faculty ID, Faculty Name, Faculty Hire Date, and Course Code. Therefore, the details of any faculty member who teaches at least one course can be recorded, but a newly hired faculty member who has not yet been assigned to teach any courses cannot be recorded, except by setting the Course Code to <a href="Null_(SQL)" title="Null (SQL)">null</a>.</dd>

<dt>Update anomaly</dt>

<dd>The same information can be expressed on multiple rows; therefore updates to the relation may result in logical inconsistencies. For example, each record in an "Employees' Skills" relation might contain an Employee ID, Employee Address, and Skill; thus a change of address for a particular employee may need to be applied to multiple records (one for each skill). If the update is only partially successful – the employee's address is updated on some records but not others – then the relation is left in an inconsistent state. Specifically, the relation provides conflicting answers to the question of what this particular employee's address is.</dd>

<dt>Deletion anomaly</dt>

<dd>Under certain circumstances, the deletion of data representing certain facts necessitates the deletion of data representing completely different facts. The "Faculty and Their Courses" relation described in the previous example suffers from this type of anomaly, for if a faculty member temporarily ceases to be assigned to any courses, the last of the records on which that faculty member appears must be deleted, effectively also deleting the faculty member, unless the Course Code field is set to null.</dd></dl>

<div class="mw-heading mw-heading3"><h3 id="Minimize_redesign_when_extending_the_database_structure">Minimize redesign when extending the database structure</h3></div>

<p>A fully normalized database allows its structure to be extended to accommodate new types of data without changing existing structure too much. As a result, applications interacting with the database are minimally affected.

</p><p>Normalized relations, and the relationship between one normalized relation and another, mirror real-world concepts and their interrelationships.

</p>

<div class="mw-heading mw-heading2"><h2 id="Normal_forms">Normal forms</h2></div>

<p>Codd introduced the concept of normalization and what is now known as the <a href="First_normal_form" title="First normal form">first normal form</a> (1NF) in 1970.<sup id="cite_ref-Codd1970_4-0" class="reference"><a href="#cite_note-Codd1970-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Codd went on to define the <a href="Second_normal_form" title="Second normal form">second normal form</a> (2NF) and <a href="Third_normal_form" title="Third normal form">third normal form</a> (3NF) in 1971,<sup id="cite_ref-Codd,_E.F_1971_5-0" class="reference"><a href="#cite_note-Codd,_E.F_1971-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> and Codd and <a href="Raymond_F._Boyce" title="Raymond F. Boyce">Raymond F. Boyce</a> defined the <a href="Boyce%E2%80%93Codd_normal_form" title="Boyce–Codd normal form">Boyce–Codd normal form</a> (BCNF) in 1974.<sup id="cite_ref-CoddBCNF_6-0" class="reference"><a href="#cite_note-CoddBCNF-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup>

</p><p><a href="Ronald_Fagin" title="Ronald Fagin">Ronald Fagin</a> introduced the <a href="Fourth_normal_form" title="Fourth normal form">fourth normal form</a> (4NF) in 1977 and the <a href="Fifth_normal_form" title="Fifth normal form">fifth normal form</a> (5NF) in 1979. <a href="Christopher_J._Date" title="Christopher J. Date">Christopher J. Date</a> introduced the <a href="Sixth_normal_form" title="Sixth normal form">sixth normal form</a> (6NF) in 2003.

</p><p>Informally, a relational database relation is often described as "normalized" if it meets third normal form.<sup id="cite_ref-DateIntroDBSys_7-0" class="reference"><a href="#cite_note-DateIntroDBSys-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Most 3NF relations are free of insertion, updation, and deletion anomalies.

</p><p>The normal forms (from least normalized to most normalized) are:

</p>

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<ul><li>UNF: <a href="Unnormalized_form" title="Unnormalized form">Unnormalized form</a></li>

<li>1NF: <a href="First_normal_form" title="First normal form">First normal form</a></li>

<li>2NF: <a href="Second_normal_form" title="Second normal form">Second normal form</a></li>

<li>3NF: <a href="Third_normal_form" title="Third normal form">Third normal form</a></li>

<li>EKNF: <a href="Elementary_key_normal_form" title="Elementary key normal form">Elementary key normal form</a></li>

<li>BCNF: <a href="Boyce%E2%80%93Codd_normal_form" title="Boyce–Codd normal form">Boyce–Codd normal form</a></li>

<li>4NF: <a href="Fourth_normal_form" title="Fourth normal form">Fourth normal form</a></li>

<li>ETNF: <a href="Essential_tuple_normal_form" title="Essential tuple normal form">Essential tuple normal form</a></li>

<li>5NF: <a href="Fifth_normal_form" title="Fifth normal form">Fifth normal form</a></li>

<li>DKNF: <a href="Domain-key_normal_form" title="Domain-key normal form">Domain-key normal form</a></li>

<li>6NF: <a href="Sixth_normal_form" title="Sixth normal form">Sixth normal form</a></li></ul></div>

<th>Constraint<br><span style="font-weight:normal"><span style="font-size: 85%;">(informal description in parentheses)</span></span>

</th>

</th>

</th>

</th>

</th>

</th>

</th>

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</th>

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<td>Unique rows (no duplicate records)<sup id="cite_ref-Codd1970_4-1" class="reference"><a href="#cite_note-Codd1970-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup></td>

</td></tr>

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<td>Scalar columns (columns cannot contain relations or composite values)<sup id="cite_ref-Codd,_E.F_1971_5-1" class="reference"><a href="#cite_note-Codd,_E.F_1971-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></td>

</td></tr>

<tr>

<td>Every non-prime attribute has a full <a href="Functional_dependency" title="Functional dependency">functional dependency</a> on each <a href="Candidate_key" title="Candidate key">candidate key</a> (attributes depend on the <i>whole</i> of every key)<sup id="cite_ref-Codd,_E.F_1971_5-2" class="reference"><a href="#cite_note-Codd,_E.F_1971-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></td>

</td></tr>

<tr>

<td>Every non-trivial functional dependency either begins with a <a href="Superkey" title="Superkey">superkey</a> or ends with a prime attribute (attributes depend <i>only</i> on candidate keys)<sup id="cite_ref-Codd,_E.F_1971_5-3" class="reference"><a href="#cite_note-Codd,_E.F_1971-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></td>

</td></tr>

<tr>

<td>Every non-trivial functional dependency either begins with a superkey or ends with an <a href="Elementary_key_normal_form" title="Elementary key normal form">elementary prime attribute</a> (a stricter form of 3NF)</td>

<td data-sort-value="" style="background: var(--background-color-interactive, #ececec); color: var(--color-base, inherit); vertical-align: middle; text-align: center;" class="table-na">—

</td></tr>

<tr>

<td>Every non-trivial functional dependency begins with a superkey (a stricter form of 3NF)</td>

<td data-sort-value="" style="background: var(--background-color-interactive, #ececec); color: var(--color-base, inherit); vertical-align: middle; text-align: center;" class="table-na">—

</td></tr>

<tr>

<td>Every non-trivial <a href="Multivalued_dependency" title="Multivalued dependency">multivalued dependency</a> begins with a superkey</td>

<td data-sort-value="" style="background: var(--background-color-interactive, #ececec); color: var(--color-base, inherit); vertical-align: middle; text-align: center;" class="table-na">—

</td></tr>

<tr>

<td>Every <a href="Join_dependency" title="Join dependency">join dependency</a> has a superkey component<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup></td>

<td data-sort-value="" style="background: var(--background-color-interactive, #ececec); color: var(--color-base, inherit); vertical-align: middle; text-align: center;" class="table-na">—

</td></tr>

<tr>

<td>Every join dependency has only superkey components</td>

<td data-sort-value="" style="background: var(--background-color-interactive, #ececec); color: var(--color-base, inherit); vertical-align: middle; text-align: center;" class="table-na">—

</td></tr>

<tr>

<td>Every constraint is a consequence of domain constraints and key constraints</td>

</td></tr>

<tr>

<td>Every join dependency is trivial</td>

</td></tr></tbody></table>

<div class="mw-heading mw-heading2"><h2 id="Example_of_a_step-by-step_normalization">Example of a step-by-step normalization</h2></div>

<p>Normalization is a database design technique, which is used to design a <a href="Relational_database" title="Relational database">relational database</a> table up to higher normal form.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> The process is progressive, and a higher level of database normalization cannot be achieved unless the previous levels have been satisfied.<sup id="cite_ref-:0_10-0" class="reference"><a href="#cite_note-:0-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup>

</p><p>That means that, having data in <a href="Unnormalized_form" title="Unnormalized form">unnormalized form</a> (the least normalized) and aiming to achieve the highest level of normalization, the first step would be to ensure compliance to <a href="First_normal_form" title="First normal form">first normal form</a>, the second step would be to ensure <a href="Second_normal_form" title="Second normal form">second normal form</a> is satisfied, and so forth in order mentioned above, until the data conforms to <a href="Sixth_normal_form" title="Sixth normal form">sixth normal form</a>.

</p><p>However, normal forms beyond <a href="4NF" class="mw-redirect" title="4NF">4NF</a> are mainly of academic interest, as the problems they exist to solve rarely appear in practice.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup>

</p><p><i>The data in the following example was intentionally designed to contradict most of the normal forms. In practice it is often possible to skip some of the normalization steps because the data is already normalized to some extent. Fixing a violation of one normal form also often fixes a violation of a higher normal form. In the example, one table has been chosen for normalization at each step, meaning that at the end, some tables might not be sufficiently normalized.</i>

</p>

<div class="mw-heading mw-heading3"><h3 id="Initial_data">Initial data</h3></div>

<p>Let a database table exist with the following structure:<sup id="cite_ref-:0_10-1" class="reference"><a href="#cite_note-:0-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup>

</p>

<th>Title

</th>

<th>Author

</th>

<th>Author Nationality

</th>

<th>Format

</th>

<th>Price

</th>

<th>Subject

</th>

<th>Pages

</th>

<th>Thickness

</th>

<th>Publisher

</th>

<th>Publisher Country

</th>

<th>Genre ID

</th>

<th>Genre Name

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Chad Russell

</td>

<td>American

</td>

<td>Hardcover

</td>

<td>49.99

</td>

<td>

<td>MySQL

</td></tr>

<tr>

<td>Database

</td></tr>

<tr>

<td>Design

</td></tr></tbody></table>

</td>

<td>520

</td>

<td>Thick

</td>

<td>Apress

</td>

<td>USA

</td>

<td>1

</td>

<td>Tutorial

</td></tr></tbody></table>

<p>For this example it is assumed that each book has only one author.

</p><p>A table that conforms to the relational model has a <a href="Primary_key" title="Primary key">primary key</a> which uniquely identifies a row. In our example, the primary key is a <a href="Composite_key" title="Composite key">composite key</a> of <b>{Title, Format}</b> (indicated by the underlining):

</p>

<th><u>Title</u>

</th>

<th>Author

</th>

<th>Author Nationality

</th>

<th><u>Format</u>

</th>

<th>Price

</th>

<th>Subject

</th>

<th>Pages

</th>

<th>Thickness

</th>

<th>Publisher

</th>

<th>Publisher Country

</th>

<th>Genre ID

</th>

<th>Genre Name

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Chad Russell

</td>

<td>American

</td>

<td>Hardcover

</td>

<td>49.99

</td>

<td>

<td>MySQL

</td></tr>

<tr>

<td>Database

</td></tr>

<tr>

<td>Design

</td></tr></tbody></table>

</td>

<td>520

</td>

<td>Thick

</td>

<td>Apress

</td>

<td>USA

</td>

<td>1

</td>

<td>Tutorial

</td></tr></tbody></table>

<div class="mw-heading mw-heading3"><h3 id="Satisfying_1NF">Satisfying 1NF</h3></div>

<p>In the <a href="First_normal_form" title="First normal form">first normal form</a> each field contains a single value. A field may not contain a set of values or a nested record. <b>Subject</b> contains a set of subject values, meaning it does not comply. To solve the problem, the subjects are extracted into a separate <b>Subject</b> table:<sup id="cite_ref-:0_10-2" class="reference"><a href="#cite_note-:0-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup>

</p>

<caption>Book

</caption>

<th><u>Title</u>

</th>

<th>Author

</th>

<th>Author Nationality

</th>

<th><u>Format</u>

</th>

<th>Price

</th>

<th>Pages

</th>

<th>Thickness

</th>

<th>Publisher

</th>

<th>Publisher Country

</th>

<th>Genre ID

</th>

<th>Genre Name

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Chad Russell

</td>

<td>American

</td>

<td>Hardcover

</td>

<td>49.99

</td>

<td>520

</td>

<td>Thick

</td>

<td>Apress

</td>

<td>USA

</td>

<td>1

</td>

<td>Tutorial

</td></tr></tbody></table>

<caption><b>Title - Subject</b>

</caption>

<th><b><u>Title</u></b>

</th>

<th><b><u>Subject name</u></b>

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>MySQL

</td></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Database

</td></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Design

</td></tr></tbody></table>

<p>Instead of one table in <a href="Unnormalized_form" title="Unnormalized form">unnormalized form</a>, there are now two tables conforming to the 1NF.

</p>

<div class="mw-heading mw-heading3"><h3 id="Satisfying_2NF">Satisfying 2NF</h3></div>

<p>Recall that the <b>Book</b> table below has a <a href="Composite_key" title="Composite key">composite key</a> of <b>{Title, Format}</b>, which will not satisfy 2NF if some subset of that key is a determinant. At this point in our design the <b>key</b> is not finalized as the <a href="Primary_key" title="Primary key">primary key</a>, so it is called a <a href="Candidate_key" title="Candidate key">candidate key</a>. Consider the following table:

</p>

<caption>Book

</caption>

<th><u>Title</u>

</th>

<th><u>Format</u>

</th>

<th>Author

</th>

<th>Author Nationality

</th>

<th>Price

</th>

<th>Pages

</th>

<th>Thickness

</th>

<th>Publisher

</th>

<th>Publisher Country

</th>

<th>Genre ID

</th>

<th>Genre Name

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Hardcover

</td>

<td>Chad Russell

</td>

<td>American

</td>

<td>49.99

</td>

<td>520

</td>

<td>Thick

</td>

<td>Apress

</td>

<td>USA

</td>

<td>1

</td>

<td>Tutorial

</td></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>E-book

</td>

<td>Chad Russell

</td>

<td>American

</td>

<td>22.34

</td>

<td>520

</td>

<td>Thick

</td>

<td>Apress

</td>

<td>USA

</td>

<td>1

</td>

<td>Tutorial

</td></tr>

<tr>

<td>The Relational Model for Database Management: Version 2

</td>

<td>E-book

</td>

<td>E.F.Codd

</td>

<td>British

</td>

<td>13.88

</td>

<td>538

</td>

<td>Thick

</td>

<td>Addison-Wesley

</td>

<td>USA

</td>

<td>2

</td>

<td>Popular science

</td></tr>

<tr>

<td>The Relational Model for Database Management: Version 2

</td>

<td>Paperback

</td>

<td>E.F.Codd

</td>

<td>British

</td>

<td>39.99

</td>

<td>538

</td>

<td>Thick

</td>

<td>Addison-Wesley

</td>

<td>USA

</td>

<td>2

</td>

<td>Popular science

</td></tr></tbody></table>

<p>All of the attributes that are not part of the candidate key depend on <i>Title</i>, but only <i>Price</i> also depends on <i>Format</i>. To conform to <a href="Second_normal_form" title="Second normal form">2NF</a> and remove duplicates, every non-candidate-key attribute must depend on the whole candidate key, not just part of it.

</p><p>To normalize this table, make <b>{Title}</b> a (simple) candidate key (the primary key) so that every non-candidate-key attribute depends on the whole candidate key, and remove <i>Price</i> into a separate table so that its dependency on <i>Format</i> can be preserved:

</p>

<caption>Book

</caption>

<th><u>Title</u>

</th>

<th>Author

</th>

<th>Author Nationality

</th>

<th>Pages

</th>

<th>Thickness

</th>

<th>Publisher

</th>

<th>Publisher Country

</th>

<th>Genre ID

</th>

<th>Genre Name

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Chad Russell

</td>

<td>American

</td>

<td>520

</td>

<td>Thick

</td>

<td>Apress

</td>

<td>USA

</td>

<td>1

</td>

<td>Tutorial

</td></tr>

<tr>

<td>The Relational Model for Database Management: Version 2

</td>

<td>E.F.Codd

</td>

<td>British

</td>

<td>538

</td>

<td>Thick

</td>

<td>Addison-Wesley

</td>

<td>USA

</td>

<td>2

</td>

<td>Popular science

</td></tr></tbody></table>

<caption>Price

</caption>

<th><u>Title</u>

</th>

<th><u>Format</u>

</th>

<th>Price

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Hardcover

</td>

<td>49.99

</td></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>E-book

</td>

<td>22.34

</td></tr>

<tr>

<td>The Relational Model for Database Management: Version 2

</td>

<td>E-book

</td>

<td>13.88

</td></tr>

<tr>

<td>The Relational Model for Database Management: Version 2

</td>

<td>Paperback

</td>

<td>39.99

</td></tr></tbody></table>

<p>Now, both the <b>Book</b> and <b>Price</b> tables conform to <a href="Second_normal_form" title="Second normal form">2NF</a>.

</p>

<div class="mw-heading mw-heading3"><h3 id="Satisfying_3NF">Satisfying 3NF</h3></div>

<p>The <b>Book</b> table still has a transitive functional dependency ({Author Nationality} is dependent on {Author}, which is dependent on {Title}). Similar violations exist for publisher ({Publisher Country} is dependent on {Publisher}, which is dependent on {Title}) and for genre ({Genre Name} is dependent on {Genre ID}, which is dependent on {Title}). Hence, the <b>Book</b> table is not in 3NF. To resolve this, we can place {Author Nationality}, {Publisher Country}, and {Genre Name} in their own respective tables, thereby eliminating the transitive functional dependencies:

</p>

<caption>Book

</caption>

<th><u>Title</u>

</th>

<th>Author

</th>

<th>Pages

</th>

<th>Thickness

</th>

<th>Publisher

</th>

<th>Genre ID

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Chad Russell

</td>

<td>520

</td>

<td>Thick

</td>

<td>Apress

</td>

<td>1

</td></tr>

<tr>

<td>The Relational Model for Database Management: Version 2

</td>

<td>E.F.Codd

</td>

<td>538

</td>

<td>Thick

</td>

<td>Addison-Wesley

</td>

<td>2

</td></tr></tbody></table>

<table>

<td>

<caption>Price

</caption>

<th><u>Title</u>

</th>

<th><u>Format</u>

</th>

<th>Price

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Hardcover

</td>

<td>49.99

</td></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>E-book

</td>

<td>22.34

</td></tr>

<tr>

<td>The Relational Model for Database Management: Version 2

</td>

<td>E-book

</td>

<td>13.88

</td></tr>

<tr>

<td>The Relational Model for Database Management: Version 2

</td>

<td>Paperback

</td>

<td>39.99

</td></tr></tbody></table>

<caption>Author

</caption>

<th><u>Author</u>

</th>

<th>Nationality

</th></tr>

<tr>

<td>Chad Russell

</td>

<td>American

</td></tr>

<tr>

<td>E.F.Codd

</td>

<td>British

</td></tr></tbody></table>

<caption>Publisher

</caption>

<th><u>Publisher</u>

</th>

<th>Country

</th></tr>

<tr>

<td>Apress

</td>

<td>USA

</td></tr>

<tr>

<td>Addison-Wesley

</td>

<td>USA

</td></tr></tbody></table>

<caption>Genre

</caption>

<th><u>Genre ID</u>

</th>

<th>Name

</th></tr>

<tr>

<td>1

</td>

<td>Tutorial

</td></tr>

<tr>

<td>2

</td>

<td>Popular science

</td></tr></tbody></table>

<div class="mw-heading mw-heading3"><h3 id="Satisfying_EKNF">Satisfying EKNF</h3></div>

/* start https://en.wikipedia.org/ */

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</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Elementary_key_normal_form" title="Elementary key normal form">Elementary key normal form</a></div>

<p>The elementary key normal form (EKNF) falls strictly between 3NF and BCNF and is not much discussed in the literature. It is intended <i>"to capture the salient qualities of both 3NF and BCNF"</i> while avoiding the problems of both (namely, that 3NF is "too forgiving" and BCNF is "prone to computational complexity"). Since it is rarely mentioned in literature, it is not included in this example.

</p>

<div class="mw-heading mw-heading3"><h3 id="Satisfying_4NF">Satisfying 4NF</h3></div>

<p>Assume the database is owned by a book retailer franchise that has several franchisees that own shops in different locations. And therefore the retailer decided to add a table that contains data about availability of the books at different locations:

</p>

<caption align="top"><b>Franchisee - Book - Location</b>

</caption>

<th><u>Franchisee ID</u>

</th>

<th><u>Title</u>

</th>

<th><u>Location</u>

</th></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>California

</td></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Florida

</td></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Texas

</td></tr>

<tr>

<td>1

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>California

</td></tr>

<tr>

<td>1

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>Florida

</td></tr>

<tr>

<td>1

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>Texas

</td></tr>

<tr>

<td>2

</td>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>California

</td></tr>

<tr>

<td>2

</td>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Florida

</td></tr>

<tr>

<td>2

</td>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Texas

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>California

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>Florida

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>Texas

</td></tr>

<tr>

<td>3

</td>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>Texas

</td></tr>

</tbody></table>

<p>As this table structure consists of a <a href="Compound_key" class="mw-redirect" title="Compound key">compound primary key</a>, it doesn't contain any non-key attributes and it's already in <a href="Boyce%E2%80%93Codd_normal_form" title="Boyce–Codd normal form">BCNF</a> (and therefore also satisfies all the previous <a class="mw-selflink-fragment" href="#Normal_forms">normal forms</a>). However, assuming that all available books are offered in each area, the <b>Title</b> is not unambiguously bound to a certain <b>Location</b> and therefore the table doesn't satisfy <a href="Fourth_normal_form" title="Fourth normal form">4NF</a>.

</p><p>That means that, to satisfy the <a href="Fourth_normal_form" title="Fourth normal form">fourth normal form</a>, this table needs to be decomposed as well:

</p>

<table>

<td>

<caption align="top"><b>Franchisee - Book</b>

</caption>

<th><u>Franchisee ID</u>

</th>

<th><u>Title</u>

</th></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td></tr>

<tr>

<td>1

</td>

<td>The Relational Model for Database Management: Version 2

</td></tr>

<tr>

<td>2

</td>

<td>Beginning MySQL Database Design and Optimization

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td></tr>

<tr>

<td>3

</td>

<td>Beginning MySQL Database Design and Optimization

</td></tr>

</tbody></table>

</td>

<td>

<caption align="top">Franchisee - Location

</caption>

<th><u>Franchisee ID</u>

</th>

<th><u>Location</u>

</th></tr>

<tr>

<td>1

</td>

<td>California

</td></tr>

<tr>

<td>1

</td>

<td>Florida

</td></tr>

<tr>

<td>1

</td>

<td>Texas

</td></tr>

<tr>

<td>2

</td>

<td>California

</td></tr>

<tr>

<td>2

</td>

<td>Florida

</td></tr>

<tr>

<td>2

</td>

<td>Texas

</td></tr>

<tr>

<td>3

</td>

<td>Texas

</td></tr>

</tbody></table>

</td></tr></tbody></table>

<p>Now, every record is unambiguously identified by a <a href="Superkey" title="Superkey">superkey</a>, therefore <a href="4NF" class="mw-redirect" title="4NF">4NF</a> is satisfied.

</p>

<div class="mw-heading mw-heading3"><h3 id="Satisfying_ETNF">Satisfying ETNF</h3></div>

<p>Suppose the franchisees can also order books from different suppliers. Let the relation also be subject to the following constraint:

</p>

<ul><li>If a certain <b>supplier</b> supplies a certain <b>title</b></li>

<li>and the <b>title</b> is supplied to the <b>franchisee</b></li>

<li>and the <b>franchisee</b> is being supplied by the <b>supplier,</b></li>

<li>then the <b>supplier</b> supplies the <b>title</b> to the <b>franchisee</b>.<sup id="cite_ref-:2_12-0" class="reference"><a href="#cite_note-:2-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup></li></ul>

<caption>Supplier - Book - Franchisee

</caption>

<th><u>Supplier ID</u>

</th>

<th><u>Title</u>

</th>

<th><u>Franchisee ID</u>

</th></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>1

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>2

</td></tr>

<tr>

<td>3

</td>

<td>Learning SQL

</td>

<td>3

</td></tr></tbody></table>

<p>This table is in <a href="Fourth_normal_form" title="Fourth normal form">4NF</a>, but the Supplier ID is equal to the join of its projections: <b>{{Supplier ID, Title}, {Title, Franchisee ID}, {Franchisee ID, Supplier ID}}.</b> No component of that join dependency is a <a href="Superkey" title="Superkey">superkey</a> (the sole superkey being the entire heading), so the table does not satisfy the <a href="Essential_tuple_normal_form" title="Essential tuple normal form">ETNF</a> and can be further decomposed:<sup id="cite_ref-:2_12-1" class="reference"><a href="#cite_note-:2-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup>

</p>

<table>

<td>

<caption>Supplier - Book

</caption>

<th><u>Supplier ID</u>

</th>

<th><u>Title</u>

</th></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td></tr>

<tr>

<td>3

</td>

<td>Learning SQL

</td></tr></tbody></table>

</td>

<td>

<caption>Book - Franchisee

</caption>

<th><u>Title</u>

</th>

<th><u>Franchisee ID</u>

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>1

</td></tr>

<tr>

<td>The Relational Model for Database Management: Version 2

</td>

<td>2

</td></tr>

<tr>

<td>Learning SQL

</td>

<td>3

</td></tr></tbody></table>

</td>

<td>

<caption>Franchisee - Supplier

</caption>

<th><u>Supplier ID</u>

</th>

<th><u>Franchisee ID</u>

</th></tr>

<tr>

<td>1

</td>

<td>1

</td></tr>

<tr>

<td>2

</td>

<td>2

</td></tr>

<tr>

<td>3

</td>

<td>3

</td></tr></tbody></table>

<p>The decomposition produces ETNF compliance.

</p>

<div class="mw-heading mw-heading3"><h3 id="Satisfying_5NF">Satisfying 5NF</h3></div>

<p>To spot a table not satisfying the <a href="Fifth_normal_form" title="Fifth normal form">5NF</a>, it is usually necessary to examine the data thoroughly. Suppose the table from <a class="mw-selflink-fragment" href="#Satisfying_4NF">4NF example</a> with a little modification in data and let's examine if it satisfies <a href="Fifth_normal_form" title="Fifth normal form">5NF</a>:

</p>

<caption align="top"><b>Franchisee - Book - Location</b>

</caption>

<th><u>Franchisee ID</u>

</th>

<th><u>Title</u>

</th>

<th><u>Location</u>

</th></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>California

</td></tr>

<tr>

<td>1

</td>

<td>Learning SQL

</td>

<td>California

</td></tr>

<tr>

<td>1

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>Texas

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>California

</td></tr>

</tbody></table>

<p>Decomposing this table lowers redundancies, resulting in the following two tables:

</p>

<table>

<td>

<caption align="top"><b>Franchisee - Book</b>

</caption>

<th><u>Franchisee ID</u>

</th>

<th><u>Title</u>

</th></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td></tr>

<tr>

<td>1

</td>

<td>Learning SQL

</td></tr>

<tr>

<td>1

</td>

<td>The Relational Model for Database Management: Version 2

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td></tr>

</tbody></table>

</td>

<td>

<caption align="top"><b>Franchisee - Location</b>

</caption>

<th><u>Franchisee ID</u>

</th>

<th><u>Location</u>

</th></tr>

<tr>

<td>1

</td>

<td>California

</td></tr>

<tr>

<td>1

</td>

<td>Texas

</td></tr>

<tr>

<td>2

</td>

<td>California

</td></tr>

</tbody></table>

</td></tr></tbody></table>

<p>The query joining these tables would return the following data:

</p>

<caption align="top"><b>Franchisee - Book - Location JOINed</b>

</caption>

<th><u>Franchisee ID</u>

</th>

<th><u>Title</u>

</th>

<th><u>Location</u>

</th></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>California

</td></tr>

<tr>

<td>1

</td>

<td>Learning SQL

</td>

<td>California

</td></tr>

<tr>

</td>

<td><span style="color:red">The Relational Model for Database Management: Version 2</span>

</td>

<td><span style="color:red">California</span>

</td></tr>

<tr>

<td>1

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>Texas

</td></tr>

<tr>

</td>

<td><span style="color:red">Learning SQL</span>

</td>

<td><span style="color:red">Texas</span>

</td></tr>

<tr>

</td>

<td><span style="color:red">Beginning MySQL Database Design and Optimization</span>

</td>

<td><span style="color:red">Texas</span>

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>California

</td></tr>

</tbody></table>

<p>The JOIN returns three more rows than it should; adding another table to clarify the relation results in three separate tables:

<br>

</p>

<table>

<td>

<caption align="top"><b>Franchisee - Book</b>

</caption>

<th><u>Franchisee ID</u>

</th>

<th><u>Title</u>

</th></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td></tr>

<tr>

<td>1

</td>

<td>Learning SQL

</td></tr>

<tr>

<td>1

</td>

<td>The Relational Model for Database Management: Version 2

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td></tr>

</tbody></table>

</td>

<td>

<caption align="top"><b>Franchisee - Location</b>

</caption>

<th><u>Franchisee ID</u>

</th>

<th><u>Location</u>

</th></tr>

<tr>

<td>1

</td>

<td>California

</td></tr>

<tr>

<td>1

</td>

<td>Texas

</td></tr>

<tr>

<td>2

</td>

<td>California

</td></tr>

</tbody></table>

</td>

<td>

<caption align="top"><b>Location - Book</b>

</caption>

<th><u>Location</u>

</th>

<th><u>Title</u>

</th></tr>

<tr>

<td>California

</td>

<td>Beginning MySQL Database Design and Optimization

</td></tr>

<tr>

<td>California

</td>

<td>Learning SQL

</td></tr>

<tr>

<td>California

</td>

<td>The Relational Model for Database Management: Version 2

</td></tr>

<tr>

<td>Texas

</td>

<td>The Relational Model for Database Management: Version 2

</td></tr>

</tbody></table>

</td></tr></tbody></table>

<p>What will the JOIN return now? It actually is not possible to join these three tables. That means it wasn't possible to decompose the <b>Franchisee - Book - Location</b> without data loss, therefore the table already satisfies <a href="5NF" class="mw-redirect" title="5NF">5NF</a>.

</p><p><b>Disclaimer</b> - the data used demonstrates the principal, but fails to remain true.

In this case the data would best be decomposed into the following, with a surrogate key which we will call 'Store ID':

</p>

<table>

<td>

<caption align="top"><b>Store - Book</b>

</caption>

<th><u>Store ID</u>

</th>

<th><u>Title</u>

</th></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td></tr>

<tr>

<td>1

</td>

<td>Learning SQL

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td></tr>

<tr>

<td>3

</td>

<td>The Relational Model for Database Management: Version 2

</td></tr>

</tbody></table>

</td>

<td>

<caption align="top"><b>Store - Franchisee - Location</b>

</caption>

<th><u>Store ID</u>

</th>

<th>Franchisee ID

</th>

<th>Location

</th></tr>

<tr>

<td>1

</td>

<td>1

</td>

<td>California

</td></tr>

<tr>

<td>2

</td>

<td>1

</td>

<td>Texas

</td></tr>

<tr>

<td>3

</td>

<td>2

</td>

<td>California

</td></tr>

</tbody></table>

</td>

<td>

</td></tr></tbody></table>

<p>The JOIN will now return the expected result:

</p>

<caption align="top"><b>Store - Book - Franchisee - Location JOINed</b>

</caption>

<th><u>Store ID</u>

</th>

<th><u>Title</u>

</th>

<th><u>Franchisee ID</u>

</th>

<th><u>Location</u>

</th></tr>

<tr>

<td>1

</td>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>1

</td>

<td>California

</td></tr>

<tr>

<td>1

</td>

<td>Learning SQL

</td>

<td>1

</td>

<td>California

</td></tr>

<tr>

<td>2

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>1

</td>

<td>Texas

</td></tr>

<tr>

<td>3

</td>

<td>The Relational Model for Database Management: Version 2

</td>

<td>2

</td>

<td>California

</td></tr>

</tbody></table>

<p><br>

<a href="Christopher_J._Date" title="Christopher J. Date">C.J. Date</a> has argued that only a database in 5NF is truly "normalized".<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup>

</p>

<div class="mw-heading mw-heading3"><h3 id="Satisfying_DKNF">Satisfying DKNF</h3></div>

<p>Let's have a look at the <b>Book</b> table from previous examples and see if it satisfies the <a href="Domain-key_normal_form" title="Domain-key normal form">domain-key normal form</a>:

</p>

<caption>Book

</caption>

<th><u>Title</u>

</th>

<th><b>Pages</b>

</th>

<th>Thickness

</th>

<th><i>Genre ID</i>

</th>

<th><i>Publisher ID</i>

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>520

</td>

<td>Thick

</td>

</td>

</td></tr>

<tr>

<td>The Relational Model for Database Management: Version 2

</td>

<td>538

</td>

<td>Thick

</td>

</td>

</td></tr>

<tr>

<td>Learning SQL

</td>

<td>338

</td>

<td>Slim

</td>

</td>

</td></tr>

<tr>

<td>SQL Cookbook

</td>

<td>636

</td>

<td>Thick

</td>

</td>

</td></tr></tbody></table>

<p>Logically, <b>Thickness</b> is determined by number of pages. That means it depends on <b>Pages</b> which is not a key. Let's set an example convention saying a book up to 350 pages is considered "slim" and a book over 350 pages is considered "thick".

</p><p>This convention is technically a constraint but it is neither a domain constraint nor a key constraint; therefore we cannot rely on domain constraints and key constraints to keep the data integrity.

</p><p>In other words – nothing prevents us from putting, for example, "Thick" for a book with only 50 pages – and this makes the table violate <a href="Domain-key_normal_form" title="Domain-key normal form">DKNF</a>.

</p><p>To solve this, a table holding enumeration that defines the <b>Thickness</b> is created, and that column is removed from the original table:

</p>

<table>

<td>

<caption>Thickness Enum

</caption>

<th><u>Thickness</u>

</th>

<th>Min pages

</th>

<th>Max pages

</th></tr>

<tr>

<td>Slim

</td>

<td>1

</td>

<td>350

</td></tr>

<tr>

<td>Thick

</td>

<td>351

</td>

<td>999,999,999,999

</td></tr></tbody></table>

</td>

<td>

<caption>Book - Pages - Genre - Publisher

</caption>

<th><u>Title</u>

</th>

<th>Pages

</th>

<th><i>Genre ID</i>

</th>

<th><i>Publisher ID</i>

</th></tr>

<tr>

<td>Beginning MySQL Database Design and Optimization

</td>

<td>520

</td>

</td>

</td></tr>

<tr>

<td>The Relational Model for Database Management: Version 2

</td>

<td>538

</td>

</td>

</td></tr>

<tr>

<td>Learning SQL

</td>

<td>338

</td>

</td>

</td></tr>

<tr>

<td>SQL Cookbook

</td>

<td>636

</td>

</td>

</td></tr></tbody></table>

<p>That way, the domain integrity violation has been eliminated, and the table is in <a href="Domain-key_normal_form" title="Domain-key normal form">DKNF</a>.

</p>

<div class="mw-heading mw-heading3"><h3 id="Satisfying_6NF">Satisfying 6NF</h3></div>

<p>A simple and intuitive definition of the <a href="Sixth_normal_form" title="Sixth normal form">sixth normal form</a> is that <i>"a table is in <a href="Sixth_normal_form" title="Sixth normal form">6NF</a> when <b>the row contains the Primary Key, and at most one other attribute"</b></i><b>.</b><sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup>

</p><p>That means, for example, the <b>Publisher</b> table designed while <a href="#Satisfying_1NF">creating the 1NF</a>:

</p>

<caption>Publisher

</caption>

<th>Publisher ID

</th>

<th>Name

</th>

<th>Country

</th></tr>

<tr>

<td>1

</td>

<td>Apress

</td>

<td>USA

</td></tr></tbody></table>

<p>needs to be further decomposed into two tables:

</p>

<table>

<td>

<caption>Publisher

</caption>

<th>Publisher ID

</th>

<th>Name

</th></tr>

<tr>

<td>1

</td>

<td>Apress

</td></tr></tbody></table>

</td>

<td>

<caption>Publisher country

</caption>

<th>Publisher ID

</th>

<th>Country

</th></tr>

<tr>

<td>1

</td>

<td>USA

</td></tr></tbody></table>

<p>The obvious drawback of 6NF is the proliferation of tables required to represent the information on a single entity. If a table in 5NF has one primary key column and N attributes, representing the same information in 6NF will require N tables; multi-field updates to a single conceptual record will require updates to multiple tables; and inserts and deletes will similarly require operations across multiple tables. For this reason, in databases intended to serve <a href="Online_transaction_processing" title="Online transaction processing">online transaction processing</a> (OLTP) needs, 6NF should not be used.

</p><p>However, in <a href="Data_warehouses" class="mw-redirect" title="Data warehouses">data warehouses</a>, which do not permit interactive updates and which are specialized for fast query on large data volumes, certain DBMSs use an internal 6NF representation – known as a <a href="Column-oriented_DBMS" class="mw-redirect" title="Column-oriented DBMS">columnar data store</a>. In situations where the number of unique values of a column is far less than the number of rows in the table, column-oriented storage allow significant savings in space through data compression. Columnar storage also allows fast execution of range queries (e.g., show all records where a particular column is between X and Y, or less than X.)

</p><p>In all these cases, however, the database designer does not have to perform 6NF normalization manually by creating separate tables. Some DBMSs that are specialized for warehousing, such as <a href="Sybase_IQ" class="mw-redirect" title="Sybase IQ">Sybase IQ</a>, use columnar storage by default, but the designer still sees only a single multi-column table. Other DBMSs, such as Microsoft SQL Server 2012 and later, let you specify a "columnstore index" for a particular table.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup>

</p>

<ul><li><a href="Denormalization" title="Denormalization">Denormalization</a></li>

<li><a href="Database_refactoring" title="Database refactoring">Database refactoring</a></li>

<li><a href="Lossless_join_decomposition" title="Lossless join decomposition">Lossless join decomposition</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="Notes_and_references">Notes and references</h2></div>

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<li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text">"The adoption of a relational model of data ... permits the development of a universal data sub-language based on an applied predicate calculus. A first-order predicate calculus suffices if the collection of relations is in normal form. Such a language would provide a yardstick of linguistic power for all other proposed data languages, and would itself be a strong candidate for embedding (with appropriate syntactic modification) in a variety of host languages (programming, command- or problem-oriented)." Codd, <a rel="nofollow" class="external text" href="https://dl.acm.org/doi/10.1145/362384.362685">"A Relational Model of Data for Large Shared Data Banks"</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070612235326/http://www.acm.org/classics/nov95/toc.html">Archived</a> June 12, 2007, at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, p. 381</span>

</li>

<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text">Codd, E.F. Chapter 23, <a rel="nofollow" class="external text" href="https://dl.acm.org/doi/10.5555/77708.C1065772">"Serious Flaws in SQL"</a>, in <i>The Relational Model for Database Management: Version 2</i>. Addison-Wesley (1990), pp. 371–389</span>

</li>

<li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text">Codd, E.F. "Further Normalisation of the Data Base Relational Model", p. 34</span>

</li>

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</style><cite id="CITEREFCodd1970" class="citation journal cs1"><a href="Edgar_F._Codd" title="Edgar F. Codd">Codd, E. F.</a> (June 1970). <a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F362384.362685">"A Relational Model of Data for Large Shared Data Banks"</a>. <i><a href="Communications_of_the_ACM" title="Communications of the ACM">Communications of the ACM</a></i>. <b>13</b> (6): <span class="nowrap">377–</span>387. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F362384.362685">10.1145/362384.362685</a></span>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:207549016">207549016</a>.</cite></span>

</li>

<li id="cite_note-Codd,_E.F_1971-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-Codd,_E.F_1971_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Codd,_E.F_1971_5-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Codd,_E.F_1971_5-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Codd,_E.F_1971_5-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text">Codd, E. F. "Further Normalization of the Data Base Relational Model". (Presented at Courant Computer Science Symposia Series 6, "Data Base Systems", New York City, May 24–25, 1971.) IBM Research Report RJ909 (August 31, 1971). Republished in Randall J. Rustin (ed.), <i>Data Base Systems: Courant Computer Science Symposia Series 6</i>. Prentice-Hall, 1972.</span>

</li>

<li id="cite_note-CoddBCNF-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-CoddBCNF_6-0">^</a></b></span> <span class="reference-text">Codd, E. F. "Recent Investigations into Relational Data Base Systems". IBM Research Report RJ1385 (April 23, 1974). Republished in <i>Proc. 1974 Congress</i> (Stockholm, Sweden, 1974), N.Y.: North-Holland (1974).</span>

</li>

<li id="cite_note-DateIntroDBSys-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-DateIntroDBSys_7-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFDate1999" class="citation book cs1">Date, C. J. (1999). <i>An Introduction to Database Systems</i>. Addison-Wesley. p. 290.</cite></span>

</li>

<li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><cite id="CITEREFDarwenDateFagin2012" class="citation conference cs1">Darwen, Hugh; Date, C. J.; Fagin, Ronald (2012). <a rel="nofollow" class="external text" href="https://researcher.watson.ibm.com/researcher/files/us-fagin/icdt12.pdf">"A Normal Form for Preventing Redundant Tuples in Relational Databases"</a> <span class="cs1-format">(PDF)</span>. <i>Proceedings of the 15th International Conference on Database Theory</i>. <a rel="nofollow" class="external text" href="http://edbticdt2012.dima.tu-berlin.de/">EDBT/ICDT 2012 Joint Conference</a>. ACM International Conference Proceeding Series. <a href="Association_for_Computing_Machinery" title="Association for Computing Machinery">Association for Computing Machinery</a>. p. 114. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F2274576.2274589">10.1145/2274576.2274589</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-4503-0791-8</bdi>. <a href="OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/802369023">802369023</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20160306173449/http://researcher.watson.ibm.com/researcher/files/us-fagin/icdt12.pdf">Archived</a> <span class="cs1-format">(PDF)</span> from the original on March 6, 2016<span class="reference-accessdate">. Retrieved <span class="nowrap">May 22,</span> 2018</span>.</cite></span>

</li>

<li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><cite id="CITEREFKumarAzad2017" class="citation book cs1">Kumar, Kunal; Azad, S. K. (October 2017). "Database normalization design pattern". <i>2017 4th IEEE Uttar Pradesh Section International Conference on Electrical, Computer and Electronics (UPCON)</i>. IEEE. pp. <span class="nowrap">318–</span>322. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2Fupcon.2017.8251067">10.1109/upcon.2017.8251067</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9781538630044</bdi>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:24491594">24491594</a>.</cite></span>

</li>

<li id="cite_note-:0-10"><span class="mw-cite-backlink">^ <a href="#cite_ref-:0_10-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:0_10-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-:0_10-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20170830224213/https://www.computerweekly.com/tutorial/Database-normalization-in-MySQL-Four-quick-and-easy-steps">"Database normalization in MySQL: Four quick and easy steps"</a>. <i>ComputerWeekly.com</i>. Archived from <a rel="nofollow" class="external text" href="https://www.computerweekly.com/tutorial/Database-normalization-in-MySQL-Four-quick-and-easy-steps">the original</a> on August 30, 2017<span class="reference-accessdate">. Retrieved <span class="nowrap">March 23,</span> 2021</span>.</cite></span>

</li>

<li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://mariadb.com/kb/en/library/database-normalization-5th-normal-form-and-beyond/">"Database Normalization: 5th Normal Form and Beyond"</a>. <i>MariaDB KnowledgeBase</i><span class="reference-accessdate">. Retrieved <span class="nowrap">January 23,</span> 2019</span>.</cite></span>

</li>

<li id="cite_note-:2-12"><span class="mw-cite-backlink">^ <a href="#cite_ref-:2_12-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:2_12-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><cite id="CITEREFDate2015" class="citation book cs1">Date, C. J. (December 21, 2015). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=Jx5UCwAAQBAJ&q=etnf%20normalization&pg=PT138"><i>The New Relational Database Dictionary: Terms, Concepts, and Examples</i></a>. "O'Reilly Media, Inc.". p. 138. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9781491951699</bdi>.</cite></span>

</li>

<li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><cite id="CITEREFDate2015" class="citation book cs1">Date, C. J. (December 21, 2015). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=Jx5UCwAAQBAJ&q=etnf%20normalization&pg=PT163"><i>The New Relational Database Dictionary: Terms, Concepts, and Examples</i></a>. "O'Reilly Media, Inc.". p. 163. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9781491951699</bdi>.</cite></span>

</li>

<li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://stackoverflow.com/questions/4824714/would-like-to-understand-6nf-with-an-example">"normalization - Would like to Understand 6NF with an Example"</a>. <i>Stack Overflow</i><span class="reference-accessdate">. Retrieved <span class="nowrap">January 23,</span> 2019</span>.</cite></span>

</li>

<li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text">Microsoft Corporation. Columnstore Indexes: Overview. <a rel="nofollow" class="external free" href="https://docs.microsoft.com/en-us/sql/relational-databases/indexes/columnstore-indexes-overview">https://docs.microsoft.com/en-us/sql/relational-databases/indexes/columnstore-indexes-overview</a> . Accessed March 23, 2020.</span>

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</ol></div></div>

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<div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2></div>

<ul><li>Date, C. J. (1999), <i><a rel="nofollow" class="external text" href="https://web.archive.org/web/20050404010227/http://www.aw-bc.com/catalog/academic/product/0%2C1144%2C0321197844%2C00.html">An Introduction to Database Systems</a></i> (8th ed.). Addison-Wesley Longman. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-321-19784-4</bdi>.</li>

<li>Kent, W. (1983) <i><a rel="nofollow" class="external text" href="http://www.bkent.net/Doc/simple5.htm">A Simple Guide to Five Normal Forms in Relational Database Theory</a></i>, Communications of the ACM, vol. 26, pp. 120–125</li>

<li>H.-J. Schek, P. Pistor Data Structures for an Integrated Data Base Management and Information Retrieval System</li></ul>

<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><cite id="CITEREFKent1983" class="citation journal cs1">Kent, William (February 1983). <a rel="nofollow" class="external text" href="http://www.bkent.net/Doc/simple5.htm">"A Simple Guide to Five Normal Forms in Relational Database Theory"</a>. <i>Communications of the ACM</i>. <b>26</b> (2): <span class="nowrap">120–</span>125. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F358024.358054">10.1145/358024.358054</a></span>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:9195704">9195704</a>.</cite></li>

<li><a rel="nofollow" class="external text" href="http://databases.about.com/od/specificproducts/a/normalization.htm">Database Normalization Basics</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070205184226/http://databases.about.com/od/specificproducts/a/normalization.htm">Archived</a> February 5, 2007, at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a> by Mike Chapple (About.com)</li>

<li><a rel="nofollow" class="external text" href="http://www.databasejournal.com/sqletc/article.php/1428511">Database Normalization Intro</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110928000244/http://www.databasejournal.com/sqletc/article.php/1428511">Archived</a> September 28, 2011, at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, <a rel="nofollow" class="external text" href="http://www.databasejournal.com/sqletc/article.php/26861_1474411_1">Part 2</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110708233620/http://www.databasejournal.com/sqletc/article.php/26861_1474411_1">Archived</a> July 8, 2011, at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li>

<li><a rel="nofollow" class="external text" href="http://mikehillyer.com/articles/an-introduction-to-database-normalization/">An Introduction to Database Normalization</a> by Mike Hillyer.</li>

<li><a rel="nofollow" class="external text" href="http://phlonx.com/resources/nf3/">A tutorial on the first 3 normal forms</a> by Fred Coulson</li>

<li><a rel="nofollow" class="external text" href="http://support.microsoft.com/kb/283878">Description of the database normalization basics</a> by Microsoft</li>

<li><a rel="nofollow" class="external text" href="http://beginnersbook.com/2015/05/normalization-in-dbms/">Normalization in DBMS by Chaitanya (beginnersbook.com)</a></li>

<li><a rel="nofollow" class="external text" href="https://www.databasestar.com/normalization-in-dbms/">A Step-by-Step Guide to Database Normalization</a></li>

<li><a rel="nofollow" class="external text" href="http://researcher.watson.ibm.com/researcher/files/us-fagin/icdt12.pdf">ETNF – Essential tuple normal form</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20160306173449/http://researcher.watson.ibm.com/researcher/files/us-fagin/icdt12.pdf">Archived</a> March 6, 2016, at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li></ul>

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</style><div id="Database_normalization45" style="font-size:114%;margin:0 4em"></div></th></tr><tr><td colspan="2" class="navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Unnormalized_form" title="Unnormalized form">Unnormalized form</a> (UNF)</li>

<li><a href="First_normal_form" title="First normal form">First normal form</a> (1NF)</li>

<li><a href="Second_normal_form" title="Second normal form">Second normal form</a> (2NF)</li>

<li><a href="Third_normal_form" title="Third normal form">Third normal form</a> (3NF)</li>

<li><a href="Elementary_key_normal_form" title="Elementary key normal form">Elementary key normal form</a> (EKNF)</li>

<li><a href="Boyce%E2%80%93Codd_normal_form" title="Boyce–Codd normal form">Boyce–Codd normal form</a> (3.5NF / BCNF)</li>

<li><a href="Fourth_normal_form" title="Fourth normal form">Fourth normal form</a> (4NF)</li>

<li><a href="Fifth_normal_form" title="Fifth normal form">Fifth normal form</a> (5NF / PJNF)</li>

<li><a href="Domain-key_normal_form" title="Domain-key normal form">Domain-key normal form</a> (DKNF)</li>

<li><a href="Sixth_normal_form" title="Sixth normal form">Sixth normal form</a> (6NF)</li></ul>

</div></td></tr><tr><td colspan="2" class="navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"><a href="Dependency_theory_(database_theory)" title="Dependency theory (database theory)">Dependencies</a>

<ul><li><a href="Functional_dependency" title="Functional dependency">Functional dependency</a></li>

<li><a href="Multivalued_dependency" title="Multivalued dependency">Multivalued dependency</a></li>

<li><a href="Join_dependency" title="Join dependency">Join dependency</a></li>

<li><a href="Lossless_join_decomposition" title="Lossless join decomposition">Lossless join decomposition</a></li>

<li><a href="Temporal_database" title="Temporal database">Temporal database</a></li></ul></div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div><a href="Denormalization" title="Denormalization">Denormalization</a></div></td></tr></tbody></table></div>

<div class="navbox-styles"></div><div role="navigation" class="navbox" aria-labelledby="Database414" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><div id="Database414" style="font-size:114%;margin:0 4em"><a href="Database" title="Database">Database</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Main</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Database#Major_database_usage_requirements" title="Database">Requirements</a></li>

<li><a href="Database_theory" title="Database theory">Theory</a></li>

<li><a href="Database_object" title="Database object">Database object</a></li>

<li><a href="Database_model" title="Database model">Models</a></li>

<li><a href="Database_management_system" class="mw-redirect" title="Database management system">Database management system</a></li>

<li><a href="Database_machine" title="Database machine">Machine</a></li>

<li><a href="Database_engine" title="Database engine">Engine</a></li>

<li><a href="Database_server" title="Database server">Server</a></li>

<li><a href="Database_application" title="Database application">Application</a></li>

<li><a href="Database_connection" title="Database connection">Connection</a>

<ul><li><a href="Datasource" title="Datasource">datasource</a></li>

<li><a href="Database_administrator" title="Database administrator">Administrator</a></li>

<li><a href="Synonym_(database)" title="Synonym (database)">Synonym</a></li>

<li>Types</li>

<li><a href="Comparison_of_database_tools" class="mw-redirect" title="Comparison of database tools">Tools</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Database#Database_languages" title="Database">Languages</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Data_definition_language" title="Data definition language">Data definition</a></li>

<li><a href="Data_manipulation_language" title="Data manipulation language">Data manipulation</a></li>

<li><a href="Query_language" title="Query language">Query</a>

<ul><li><a href="Information_retrieval_query_language" class="mw-redirect" title="Information retrieval query language">information retrieval</a></li></ul></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Database_security" title="Database security">Security</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Database_activity_monitoring" title="Database activity monitoring">Activity monitoring</a></li>

<li><a href="Database_audit" title="Database audit">Audit</a></li>

<li><a href="Database_forensics" title="Database forensics">Forensics</a></li>

<li><a href="Negative_database" title="Negative database">Negative database</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Database_design" title="Database design">Design</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Entity%E2%80%93relationship_model" title="Entity–relationship model">Entities and relationships</a> (and <a href="Enhanced_entity%E2%80%93relationship_model" title="Enhanced entity–relationship model">Enhanced</a> notation)</li>

<li><a href="Database_schema" title="Database schema">Schema</a></li>

<li><a href="Database_refactoring" title="Database refactoring">Refactoring</a></li>

<li><a href="Cardinality_(data_modeling)" title="Cardinality (data modeling)">Cardinality</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Programming</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Database_abstraction_layer" title="Database abstraction layer">Abstraction layer</a></li>

<li><a href="Object%E2%80%93relational_mapping" title="Object–relational mapping">Object–relational mapping</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Management</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Database_virtualization" title="Database virtualization">Virtualization</a></li>

<li><a href="Database_tuning" title="Database tuning">Tuning</a>

<ul><li><a href="Database_caching" title="Database caching">caching</a></li></ul></li>

<li><a href="Data_migration#Database_migration" title="Data migration">Migration</a></li>

<li><a href="Database_preservation" title="Database preservation">Preservation</a></li>

<li><a href="Database_integrity" class="mw-redirect" title="Database integrity">Integrity</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Lists_of_databases" title="Lists of databases">Lists of</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="List_of_academic_databases_and_search_engines" title="List of academic databases and search engines">Academic</a></li>

<li><a href="List_of_biological_databases" title="List of biological databases">Biological</a></li>

<li><a href="List_of_biodiversity_databases" title="List of biodiversity databases">Biodiversity</a></li>

<li><a href="List_of_facial_expression_databases" title="List of facial expression databases">Facial expression</a></li>

<li><a href="List_of_online_databases" title="List of online databases">Online</a></li>

<li><a href="List_of_online_music_databases" title="List of online music databases">Online music</a></li>

<li><a href="List_of_online_real_estate_databases" title="List of online real estate databases">Online real estate</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">See also</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Database-centric_architecture" title="Database-centric architecture">Database-centric architecture</a></li>

<li><a href="Intelligent_database" title="Intelligent database">Intelligent database</a></li>

<li><a href="Two-phase_locking" title="Two-phase locking">Two-phase locking</a></li>

<li><a href="Locks_with_ordered_sharing" title="Locks with ordered sharing">Locks with ordered sharing</a></li>

<li><a href="Database_publishing" title="Database publishing">Publishing</a></li>

<li><a href="Halloween_Problem" title="Halloween Problem">Halloween Problem</a></li>

<li><a href="Log_shipping" title="Log shipping">Log shipping</a></li></ul>

</div></td></tr><tr><td class="navbox-abovebelow hlist" colspan="2"><div><b><span class="noviewer" typeof="mw:File"><span title="WikiProject"></span></span> WikiProject</b> <b><span class="noviewer" typeof="mw:File"><span title="Category"></span></span> Category</b></div></td></tr></tbody></table></div>

<div class="navbox-styles"></div><div role="navigation" class="navbox" aria-labelledby="Database_management_systems327" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><div id="Database_management_systems327" style="font-size:114%;margin:0 4em"><a href="Database" title="Database">Database management systems</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Types</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Object_database" title="Object database">Object-oriented</a>

<ul><li><a href="Comparison_of_object_database_management_systems" title="Comparison of object database management systems">comparison</a></li></ul></li>

<li><a href="Relational_database" title="Relational database">Relational</a>

<li><a href="Comparison_of_relational_database_management_systems" title="Comparison of relational database management systems">comparison</a></li></ul></li>

<li><a href="Key%E2%80%93value_database" title="Key–value database">Key–value</a></li>

<li><a href="Column-oriented_DBMS" class="mw-redirect" title="Column-oriented DBMS">Column-oriented</a>

<li><a href="Document-oriented_database" title="Document-oriented database">Document-oriented</a></li>

<li><a href="Wide-column_store" title="Wide-column store">Wide-column store</a></li>

<li><a href="Graph_database" title="Graph database">Graph</a></li>

<li><a href="NoSQL" title="NoSQL">NoSQL</a></li>

<li><a href="NewSQL" title="NewSQL">NewSQL</a></li>

<li><a href="In-memory_database" title="In-memory database">In-memory</a>

<li><a href="Multi-model_database" title="Multi-model database">Multi-model</a>

<ul><li><a href="Comparison_of_multi-model_databases" title="Comparison of multi-model databases">comparison</a></li></ul></li>

<li><a href="Cloud_database" title="Cloud database">Cloud</a></li>

<li><a href="Blockchain-based_database" title="Blockchain-based database">Blockchain-based database</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Concepts</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Database" title="Database">Database</a></li>

<li><a href="Armstrong's_axioms" title="Armstrong's axioms">Armstrong's axioms</a></li>

<li><a href="Codd's_12_rules" title="Codd's 12 rules">Codd's 12 rules</a></li>

<li><a href="CAP_theorem" title="CAP theorem">CAP theorem</a></li>

<li><a href="Candidate_key" title="Candidate key">Candidate key</a></li>

<li><a href="Foreign_key" title="Foreign key">Foreign key</a></li>

<li><a href="PACELC_design_principle" title="PACELC design principle">PACELC design principle</a></li>

<li><a href="Superkey" title="Superkey">Superkey</a></li>

<li><a href="Surrogate_key" title="Surrogate key">Surrogate key</a></li>

<li><a href="Unique_key" title="Unique key">Unique key</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Objects</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Relation_(database)" title="Relation (database)">Relation</a>

<ul><li><a href="Table_(database)" title="Table (database)">table</a></li>

<li><a href="Column_(database)" title="Column (database)">column</a></li>

<li><a href="Database_transaction" title="Database transaction">Transaction</a></li>

<li><a href="Transaction_log" title="Transaction log">Transaction log</a></li>

<li><a href="Database_trigger" title="Database trigger">Trigger</a></li>

<li><a href="Database_index" title="Database index">Index</a></li>

<li><a href="Stored_procedure" title="Stored procedure">Stored procedure</a></li>

<li><a href="Cursor_(databases)" title="Cursor (databases)">Cursor</a></li>

<li><a href="Partition_(database)" title="Partition (database)">Partition</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Components</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Concurrency_control" title="Concurrency control">Concurrency control</a></li>

<li><a href="Data_dictionary" title="Data dictionary">Data dictionary</a></li>

<li><a href="Query_language" title="Query language">Query language</a></li>

<li><a href="Query_optimization" title="Query optimization">Query optimizer</a></li>

<li><a href="Query_Rewriting" class="mw-redirect" title="Query Rewriting">Query rewriting system</a></li>

<li><a href="Query_plan" title="Query plan">Query plan</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Functions</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Database_administration" title="Database administration">Administration</a></li>

<li><a href="Query_optimization" title="Query optimization">Query optimization</a></li>

<li><a href="Replication_(computing)#DATABASE" title="Replication (computing)">Replication</a></li>

<li><a href="Shard_(database_architecture)" title="Shard (database architecture)">Sharding</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related topics</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Database_model" title="Database model">Database models</a></li>

<li>Database storage</li>

<li><a href="Distributed_database" title="Distributed database">Distributed database</a></li>

<li><a href="Federated_database_system" title="Federated database system">Federated database system</a></li>

<li><a href="Referential_integrity" title="Referential integrity">Referential integrity</a></li>

<li><a href="Relational_algebra" title="Relational algebra">Relational algebra</a></li>

<li><a href="Relational_calculus" title="Relational calculus">Relational calculus</a></li>

<li><a href="Relational_model" title="Relational model">Relational model</a></li>

<li><a href="Object%E2%80%93relational_database" title="Object–relational database">Object–relational database</a></li>

<li><a href="Transaction_processing" title="Transaction processing">Transaction processing</a></li></ul>

</div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div>

<ul><li><span class="noviewer" typeof="mw:File"><span title="Category"></span></span> Category</li>

<li><span class="noviewer" typeof="mw:File"><span title="Outline"></span></span> <a href="Outline_of_databases" title="Outline of databases">Outline</a></li></ul>

</div></td></tr></tbody></table></div></div><div><div class="zim-footer">

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