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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Query by Example</span></span>

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<p><b>Query by Example</b> (<b>QBE</b>) is a <a href="Database" title="Database">database</a> <a href="Query_language" title="Query language">query language</a> for <a href="Relational_database" title="Relational database">relational databases</a>.

</p>

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

<p>Query by Example was devised by Moshé M. Zloof at <a href="IBM_Research" title="IBM Research">IBM Research</a> during the mid-1970s, in parallel to the development of <a href="SQL" title="SQL">SQL</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> and influenced by the work on <a href="Relational_database" title="Relational database">relational databases</a> of <a href="Edgar_Codd" class="mw-redirect" title="Edgar Codd">Edgar Codd</a>.<sup id="cite_ref-rdbmsearlyyearsoh20070612_2-0" class="reference"><a href="#cite_note-rdbmsearlyyearsoh20070612-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> It is the first graphical query language, using visual tables where the user would enter commands, example elements and conditions. Many graphical front-ends for databases use the ideas from QBE today. Originally limited only for the purpose of <a href="Data_retrieval" title="Data retrieval">retrieving data</a>, QBE was later extended to allow other operations, such as inserts, deletes and updates, as well as creation of temporary tables.

</p><p>The motivation behind QBE is that a <a href="Parser" class="mw-redirect" title="Parser">parser</a> can convert the user's actions into statements expressed in a database manipulation language, such as <a href="SQL" title="SQL">SQL</a>. Behind the scenes, it is this statement that is actually executed. A suitably comprehensive front-end can minimize the burden on the user to remember the finer details of SQL, and it is easier and more productive for end-users (and even programmers) to select tables and columns by selecting them rather than typing in their names.

</p><p>In the context of <a href="Information_retrieval" title="Information retrieval">information retrieval</a>, QBE has a somewhat different meaning. The user can submit a document, or several documents, and ask for "similar" documents to be retrieved from a document database [see search by multiple examples<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>]. Similarity search is based comparing document vectors (see <a href="Vector_Space_Model" class="mw-redirect" title="Vector Space Model">Vector Space Model</a>).

</p><p>QBE represents seminal work in <a href="End-user_development" title="End-user development">end-user development</a>, frequently cited in research papers as an early example of this topic.

</p><p>Currently, QBE is supported in several relational database front ends, notably <a href="Microsoft_Access" title="Microsoft Access">Microsoft Access</a>, which implements "Visual Query by Example", as well as Microsoft SQL Server Enterprise Manager. It is also implemented in several <a href="Object_database" title="Object database">object-oriented databases</a> (e.g. in <a href="Db4o" title="Db4o">db4o</a><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>).

</p><p>QBE is based on the logical formalism called tableau query, although QBE adds some extensions to that, much like SQL is based on the <a href="Relational_algebra" title="Relational algebra">relational algebra</a>.

</p>

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

<p>An example using the <a href="Suppliers_and_Parts_database" title="Suppliers and Parts database">Suppliers and Parts database</a> is given here to illustrate how QBE works.

</p>

<caption>Simple QBE example

</caption>

<th>SNAME</th>

<th>OWNER</th>

<th>SCITY

</th></tr>

<tr>

<td>ROME

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

<div class="mw-heading mw-heading2"><h2 id="As_a_general_technique">As a general technique</h2></div>

<p>The term also refers to a general technique influenced by Zloof's work whereby only items with search values are used to "filter" the results. It provides a way for a software user to perform queries without having to know a query language (such as <a href="SQL" title="SQL">SQL</a>). The software can automatically generate the queries for the user (usually behind the scenes). Here are two examples based on a Contacts table with the following text (character) columns: Name, Address, City, State, and Zipcode:

</p>

<pre>Contacts Query Form - Example <b>A</b>:

.....Name: Bob

..Address:

.....City:

....State: TX

..Zipcode:

</pre>

<p>Resulting <a href="SQL" title="SQL">SQL</a>:

</p>

<div class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><pre><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">Contacts</span><span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="n">Name</span><span class="o">=</span><span class="s1">'Bob'</span><span class="w"> </span><span class="k">AND</span><span class="w"> </span><span class="k">State</span><span class="o">=</span><span class="s1">'TX'</span><span class="p">;</span>

</pre></div>

<p>Note how blank items do not generate <a href="SQL" title="SQL">SQL</a> terms. Since "Address" is blank, there is no clause generated for it.

</p>

<pre>Contacts Query Form - Example <b>B</b>:

.....Name:

..Address:

.....City: Sampleton

....State:

..Zipcode: 12345

</pre>

<p>Resulting <a href="SQL" title="SQL">SQL</a>:

</p>

<div class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><pre><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">Contacts</span><span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="n">City</span><span class="o">=</span><span class="s1">'Sampleton'</span><span class="w"> </span><span class="k">AND</span><span class="w"> </span><span class="n">Zipcode</span><span class="o">=</span><span class="s1">'12345'</span><span class="p">;</span>

</pre></div>

<p>More advanced versions of QBE have other comparison operator options, often via a pull-down menu, such as "Contains", "Not Contains", "Starts With", "Greater-Than", and so forth.

</p><p>Another approach to text comparisons is to allow one or more <a href="Wildcard_character" title="Wildcard character">wildcard character</a> characters. For example, if an asterisk is designated as a wildcard character in a particular system, then searching for last names using "Rob<b>*</b>" would return (match) last names such as "Rob", "Robert", "Robertson", "Roberto", etc.

</p>

<pre>Contacts Query Form - Example <b>C</b>:

.....Name: Rob*

..Address:

.....City:

....State:

..Zipcode:

</pre>

<p>Resulting <a href="SQL" title="SQL">SQL</a>:

</p>

<div class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><pre><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">Contacts</span><span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="n">Name</span><span class="w"> </span><span class="k">LIKE</span><span class="w"> </span><span class="s1">'Rob%'</span>

</pre></div>

<p>In standard SQL, the percent sign functions like a wildcard in a LIKE clause. In this case, the query-by-examplme form processing software would translate the asterisk to a percent sign. (An asterisk is a more common wildcard convention outside of SQL, so here the form is attempting to be more <a href="User_friendly" class="mw-redirect" title="User friendly">user friendly</a>.)

</p><p>WARNING: Query-by-example software should be careful to avoid <a href="SQL_injection" title="SQL injection">SQL injection</a>. Otherwise, devious users may penetrate further into the database than intended by builders of the query forms.

</p>

<li><a href="Microsoft_Query_by_Example" class="mw-redirect" title="Microsoft Query by Example">Microsoft Query by Example</a></li>

<li><a href="GraphQL" title="GraphQL">GraphQL</a> a QBE for JSON front-ends.</li>

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

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</style><cite id="CITEREFZloof1977" class="citation journal cs1">Zloof, M.M. (1977). "Query-by-Example: A data base language". <i>IBM Systems Journal</i>. <b>16</b> (4): <span class="nowrap">324–</span>343. <a href="CiteSeerX_(identifier)" class="mw-redirect" title="CiteSeerX (identifier)">CiteSeerX</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.86.3485">10.1.1.86.3485</a></span>. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1147%2Fsj.164.0324">10.1147/sj.164.0324</a>.</cite></span>

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<li id="cite_note-rdbmsearlyyearsoh20070612-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-rdbmsearlyyearsoh20070612_2-0">^</a></b></span> <span class="reference-text"><cite class="citation interview cs1"><a rel="nofollow" class="external text" href="https://archive.computerhistory.org/resources/access/text/2013/05/102702562-05-01-acc.pdf">"RDBMS Plenary 1: Early Years"</a> <span class="cs1-format">(PDF)</span> (Interview). Interviewed by Burton Grad. Computer History Museum. 2007-06-12. pp. <span class="nowrap">23–</span>24<span class="reference-accessdate">. Retrieved <span class="nowrap">2025-05-30</span></span>.</cite></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"><cite id="CITEREFZhuWu2014" class="citation book cs1">Zhu, Mingzhu; Wu, Yi-Fang Brook (2014-02-24). "Search by multiple examples". <i>Proceedings of the 7th ACM international conference on Web search and data mining</i>. ACM. pp. <span class="nowrap">667–</span>672. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F2556195.2556206">10.1145/2556195.2556206</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9781450323512</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:8397529">8397529</a>.</cite></span>

</li>

<li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><cite class="citation cs2">"QBE", <a rel="nofollow" class="external text" href="http://www.ibm.com/developerworks/java/library/j-db4o2.html"><i>db4o</i></a>, Developer works Java library, IBM, 27 March 2007</cite></span>

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

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<ul><li><cite id="CITEREFZloof1975" class="citation cs2">Zloof, Moshé M. (May 1975), "Query by Example", <i>National Computer Conference</i>, AFIPS Conference Proceedings, vol. 44, Anaheim, California: AFIPS Press, pp. <span class="nowrap">431–</span>8, <a href="ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0095-6880">0095-6880</a></cite>.</li>

<li><cite id="CITEREFRamakrishnanGehrke" class="citation cs2"><a href="Raghu_Ramakrishnan" title="Raghu Ramakrishnan">Ramakrishnan, Raghu</a>; <a href="Johannes_Gehrke" title="Johannes Gehrke">Gehrke, Johannes</a>, <a rel="nofollow" class="external text" href="http://www.cs.wisc.edu/~dbbook/openAccess/thirdEdition/qbe.pdf">"6. QBE"</a> <span class="cs1-format">(PDF)</span>, <i>Database Management Systems</i> (3rd ed.), Wisc</cite>.</li>

<li><cite id="CITEREFDate2004" class="citation cs2">Date, Christopher ‘Chris’ J. (2004), "8. Relational Calculus", <i>An Introduction to Database Systems</i>, Addison-Wesley Pearson, pp. <span class="nowrap">242–</span>7, <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-321-18956-1</bdi></cite>.</li>

<li><cite class="citation cs2"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20060614102510/http://searchoracle.techtarget.com/sDefinition/0,,sid41_gci214554,00.html"><i>Oracle Definitions</i></a>, Tech target, archived from <a rel="nofollow" class="external text" href="http://searchoracle.techtarget.com/sDefinition/0,,sid41_gci214554,00.html">the original</a> on 2006-06-14<span class="reference-accessdate">, retrieved <span class="nowrap">2006-06-25</span></span></cite>.</li>

<li><cite id="CITEREFZaiane1998" class="citation cs2">Zaiane, O. (1998), <a rel="nofollow" class="external text" href="http://www.cs.sfu.ca/CC/354/zaiane/material/notes/Chapter5/node2.html">"5. Query-by-Example (QBE)"</a>, <i>CC 354 notes</i>, Canada: SFI</cite>.</li></ul>

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

<ul><li><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://docs.jboss.org/hibernate/core/3.3/reference/en/html/querycriteria.html#querycriteria-examples">"Query by Example in Java using Hibernate"</a>. JBoss.</cite></li>

<li><cite id="CITEREFSoyluGieseJimenez-RuizVega-Gorgojo2015" class="citation journal cs1">Soylu, Ahmet; Giese, Martin; Jimenez-Ruiz, Ernesto; Vega-Gorgojo, Guillermo; Horrocks, Ian (2015). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20221205202950/http://www.ahmetsoylu.com/wp-content/uploads/soylu_UAIS_2016.pdf">"Experiencing OptiqueVQS: a multi-paradigm and ontology-based visual query system for end users"</a> <span class="cs1-format">(PDF)</span>. <i>Universal Access in the Information Society</i>. <b>15</b>: <span class="nowrap">129–</span>152. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs10209-015-0404-5">10.1007/s10209-015-0404-5</a>. <a href="Hdl_(identifier)" class="mw-redirect" title="Hdl (identifier)">hdl</a>:<a rel="nofollow" class="external text" href="https://hdl.handle.net/11250%2F2388519">11250/2388519</a>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:254169347">254169347</a>. Archived from <a rel="nofollow" class="external text" href="http://www.ahmetsoylu.com/wp-content/uploads/soylu_UAIS_2016.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 2022-12-05<span class="reference-accessdate">. Retrieved <span class="nowrap">2021-11-12</span></span>. <q>Visual Query System (VQS)</q></cite></li></ul></div><div><div class="zim-footer">

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