Difference between revisions 419586512 and 424708587 on enwiki

{{Unreferenced|date=April 2007}}
A <code>WHERE</code> clause in [[SQL]] specifies that a SQL [[Data Manipulation Language|Data Manipulation Language (DML)]] statement should only affect rows that meet specified criteria. The criteria are expressed in the form of predicates. <code>WHERE</code> clauses are not mandatory clauses of SQL DML statements, but should be used to limit the number of rows affected by a SQL DML statement or returned by a query.

==Overview==
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SELECT ename FROM emp WHERE ename LIKE '%A_E%';
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SQL programmers need to be aware that the LIKE predicate typically performs a search without the normal performance benefit of indexes. Using '=', '<>', etc.. instead will increase performance.  Users of the LIKE predicate should be aware that case sensitivity (e.g., 'S' versus 's') may be different based upon database product or configuration.

== External links ==

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#Move from device

#delete [http://www.psoug.org/reference/conditions.html PSOUG Home Puget Sound Oracle Users Group] gives several examples of SELECT statements with WHERE clauses.
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