Contents Index The quoted_identifier option Subqueries in search conditions

ASA SQL Reference
  SQL Language Elements

Search conditions


Function 

To specify a search condition for a WHERE clause, a HAVING clause, a CHECK clause, an ON phrase in a join, or an IF expression.

Syntax 

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 , value-expr2 [ ,value-expr3 ] ... } )
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

Parameters 

compare:
 =   |  >  |  <  |  >=  |  <=  |  <>  |  !=  |  !< |  !>

trigger-operation:
INSERTING | DELETING
UPDATING( column-name-string ) | UPDATE( column-name )

Usage 

Anywhere.

Permissions 

Must be connected to the database.

Side effects 

None.

Description 

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 the section 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.

See also 

Expressions


Subqueries in search conditions
ALL or ANY conditions
BETWEEN conditions
LIKE conditions
IN conditions
EXISTS conditions
IS NULL conditions
Truth value conditions
Trigger operation conditions
Three-valued logic
Explicit selectivity estimates

Contents Index The quoted_identifier option Subqueries in search conditions