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{{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==
<code>WHERE</code> is an [[SQL:2003|SQL]] reserved word.

The <code>WHERE</code> clause is used in conjunction with SQL DML statements, and takes the following general form:

<source lang="sql">
SQL-DML-Statement
FROM table_name 
WHERE predicate
</source>DELETE

all rows for which the predicate in the <code>WHERE</code> clause is True are affected (or returned) by the SQL DML statement or query. Rows for which the predicate evaluates to False or Unknown ([[Null (SQL)|NULL]]) are unaffected by the DML statement or query(DELETE) .⏎
⏎
The following query returns only those rows from table ''mytable'' where the value in column ''mycol'' is greater than 100.

<source lang="sql">
SELECT *
FROM   mytable
WHERE  mycol > 100
</source>DELETE t⏎
⏎
The following [[Delete (SQL)|<code>DELETE</code> statement]] removes only those rows from table ''mytable'' where the column ''mycol'' is either NULL or has a value that is equal to 100.
<source lang="sql">
DELETE
FROM   mytable
WHERE  mycol IS NULL OR mycol = 100
</source>delete

== Predicates ==
Simple predicates use one of the operators <code>=</code>, <code><></code>, <code>></code>, <code>>=</code>, <code><</code>, <code><=</code>, <code>IN</code>, <code>BETWEEN</code>, <code>LIKE</code>, <code>IS NULL</code> or <code>IS NOT NULL</code>.

(contracted; show full)
SELECT ename FROM emp WHERE ename LIKE '%A_E%';
</source>
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 ==

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.
Delete
{{SQL}}

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