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<h1>8. SQL Reference</h1>
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<a href="COMMIT_ROLLBACK.html">COMMIT WORK, ROLLBACK WORK Statement</a>
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<h2>8.18. UPDATE Statement</h2>
<p>Existing rows (or records) are changed in the database using the UPDATE statement.</p>
<p>NULL values can be utilized using the <span class="computeroutput">NULL</span> keyword without
any quotes. Since NULL is a special keyword you do not need to enclose it in single quotes, doing so
will cause it be read as a string-literal.</p>
<p>The update statement is made up by selecting the table to update, the search condition that
identifies which rows you want to update, and the <span class="computeroutput">column=value</span>
of each column you wish to change. </p>
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<p>A table can be updated using:</p>
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update demo.dba.employees e
set username = 'thing'
where email_address = 'thing@thingdom.com'
;
</pre>
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<p>It is possible to update one table based on a select from another
table. Ensure that the selection is properly conditioned to update.</p>
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update demo.dba.employees e
set username = (select U_NAME from DB.DBA.SYS_USERS u where u.U_EMAIL = e.email_address)
;
</pre>
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