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A search condition is the criteria specified for a WHERE clause, a HAVING clause, a CHECK clause, an ON phrase in a join, or an IF expression.
search-condition:
expression compare expression
| expression compare { [ ANY | SOME ] | ALL } ( subquery )
| expression IS [ NOT ] NULL
| expression [ NOT ] BETWEEN expression AND expression
| expression [ NOT ] LIKE expression [ ESCAPE expression ]
| expression [ NOT ] IN ( { expression
| subquery
| value-expr1 , ... } )
| EXISTS ( subquery )
| NOT condition
| search-condition AND search-condition
| search-condition OR search-condition
| ( search-condition )
| ( search-condition , estimate )
| search-condition IS [ NOT ] { TRUE | FALSE | UNKNOWN }
| trigger-operation
compare:
= | > | < | >= | <= | <> | != | !< | !>
trigger-operation:
INSERTING | DELETING
| UPDATING [ ( column-name-string ) ] | UPDATE( column-name )
Search conditions are used to choose a subset of the rows from a table, or in a control statement such as an IF statement to determine control of flow.
In SQL, every condition evaluates as one of TRUE, FALSE, or UNKNOWN. This is called three-valued logic. The result of a comparison is UNKNOWN if either value being compared is the NULL value. For tables displaying how logical operators combine in three-valued logic, see Three-valued logic.
Rows satisfy a search condition if and only if the result of the condition is TRUE. Rows for which the condition is UNKNOWN or FALSE do not satisfy the search condition. For more information about NULL, see NULL value.
Subqueries form an important class of expression that is used in many search conditions. For information about using subqueries in search conditions, see Subqueries in search conditions.
The different types of search condition are discussed in the following sections.
Must be connected to the database.
None.
Subqueries in search conditions
ALL, ANY, and SOME search conditions
BETWEEN search condition
LIKE search condition
IN search condition
EXISTS search condition
IS NULL and IS NOT NULL search conditions
Truth value search conditions
Trigger operation conditions
Three-valued logic
Explicit selectivity estimates