HSQLDB

<h2 id="transaction-support">Transaction support</h2>
<p>HSQLDB version 2.0 has three transaction control modes. It supports read committed and serializable <a href="/facts/Isolation_(database_systems)/DnrN4uew">transaction isolation levels</a> with table level locks or with <a href="/facts/Multiversion_concurrency_control/bktUeU82">multiversion concurrency control</a> (MVCC), or a combination of locks and MVCC. Version 1.8.1 supports transaction isolation level 0 (read uncommitted) only.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a>
</p>
<h2 id="data-storage">Data storage</h2>
<p>HSQLDB has two main table types used for durable read-write data storage, i.e., if a transaction has been successfully committed, it is guaranteed that the data will survive system failure and will keep their integrity.
</p><p>The default MEMORY type stores all data changes to the disk in the form of a <a href="/facts/SQL/UjQLJcYm">SQL</a> script. During engine start-up, these commands are executed and data are reconstructed into the memory.
</p><p>Another table type is CACHED, which allows one to store more data, at the cost of the slower performance. The HSQLDB engine loads them only partially and synchronizes the data to the disk on transaction commits. However, the engine always loads all rows affected during an update into the memory. This renders very large updates impossible without splitting the work into smaller parts.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a>
</p><p>Other table types allow access to <a href="/facts/Comma-separated_values/dv1pSR1r">comma-separated values</a> (CSV) files. These tables can participate, for example, in queries with JOINs and simplify spreadsheet processing and read-write non-durable in-memory data storage.
</p>
<h2 id="sql-features">SQL features</h2>
<p>HSQLDB 2.0 supports all the core features and many optional features of <a href="/facts/SQL%3a2008/AvdA9y8s">SQL:2008</a>. Advanced features include user-defined SQL procedures and functions, schemas, datetime intervals, updatable views, arrays, lobs, full and lateral joins and <a href="/facts/Set_operations_(SQL)/QjlI2J9Y">set operations</a>. Many non-standard functions such as TO_CHAR and DECODE are also supported. Extensions to standard SQL include user-defined <a href="/facts/Aggregate_function/685obrqz">aggregate functions</a>.
</p>
<h2 id="releases">Releases</h2>
<p>Several versions of HSQLDB have been released since 2001. Early versions were based on the discontinued HypersonicSQL database engine. Version 2.0, released in 2010, is mostly new code, written to conform to Standard <a href="/facts/SQL/UjQLJcYm">SQL</a> and <a href="/facts/Java_Database_Connectivity/uUVYg2sB">JDBC</a> 4 Specification.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a>
</p><p>Version 2.3.2 (released in 2014) is fully multi-threaded and supports high performance <a href="/facts/Two-phase_locking/A1Ezfv2n">two-phase locking</a> and <a href="/facts/Multiversion_concurrency_control/bktUeU82">MVCC (multiversion concurrency control)</a> transaction control models.
</p>
<h2 id="see-also">See also</h2>
<ul>
<li>Free and open-source software portal</li></ul>
<ul><li><a href="/facts/List_of_relational_database_management_systems/rWrTfJ7Y">List of relational database management systems</a></li>
<li><a href="/facts/Comparison_of_relational_database_management_systems/04R99cvo">Comparison of relational database management systems</a></li>
<li><a href="/facts/Apache_Derby/vSE2vVtG">Apache Derby</a></li>
<li><a href="/facts/H2_(database)/Nst23HsP">H2</a></li></ul>

<h2 id="external-links">External links</h2>
<ul><li><a href="https://hsqldb.org/">Official website</a> </li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"HSQLDB SQL Syntax". hsqldb.org. <a href="http://hsqldb.org/doc/2.0/guide/sqlgeneral-chapt.html" target="_blank">http://hsqldb.org/doc/2.0/guide/sqlgeneral-chapt.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>"PolePosition Performance Comparison". polepos.org. <a href="http://polepos.sourceforge.net/results/html/index.html" target="_blank">http://polepos.sourceforge.net/results/html/index.html</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>"Jitsi build 5390 release notes". Jitsi.org. Archived from the original on 2015-02-02. Retrieved 2015-02-01. <a href="https://web.archive.org/web/20150202001841/https://download.jitsi.org/jitsi/windows/updates/" target="_blank">https://web.archive.org/web/20150202001841/https://download.jitsi.org/jitsi/windows/updates/</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>"Software using HSQLDB". hsqldb.org. <a href="http://hsqldb.org/web/hsqlUsing.html" target="_blank">http://hsqldb.org/web/hsqlUsing.html</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>"HSQLDB Documentation". hsqldb.org. <a href="http://hsqldb.org/doc/2.0/guide/sessions-chapt.html#sqlgeneral_trans_cc-sect" target="_blank">http://hsqldb.org/doc/2.0/guide/sessions-chapt.html#sqlgeneral_trans_cc-sect</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>"HSQLDB Documentation". hsqldb.org. Archived from the original on 2015-05-02. Retrieved 2007-11-11. <a href="https://web.archive.org/web/20150502215807/http://www.hsqldb.org/doc/guide/ch05.html#N10DED" target="_blank">https://web.archive.org/web/20150502215807/http://www.hsqldb.org/doc/guide/ch05.html#N10DED</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>"The new HSQLDB". hsqldb.org. <a href="http://hsqldb.org/web/features200.html" target="_blank">http://hsqldb.org/web/features200.html</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
</ol>

HSQLDB open-in-new

HSQLDB