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SQL Anywhere 11.0.1 » SQL Anywhere Server - SQL Reference » Using SQL » SQL language elements

 

Search conditions

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. A search condition is also known as a predicate.

Syntax
search-condition :
 expression comparison-operator expression
| expression comparison-operator { [ ANY | SOME ] | ALL } ( subquery )
| expression IS [ NOT ] NULL
| expression [ NOT ] BETWEEN expression AND expression
| expression [ NOT ] LIKE pattern [ ESCAPE expression ]
| expression [ NOT ] SIMILAR TO pattern [ ESCAPE escape-expression ]
| expression [ NOT ] REGEXP pattern [ ESCAPE escape-expression ]
| expression [ NOT ] IN ( { expression
     | subquery
     | value-expression1 , ... } )
| CONTAINS (column-name [,... ] , query-string )
| EXISTS ( subquery )
| NOT condition
| search-condition [ { AND | OR } search-condition ] [ ... ]
| ( search-condition )
| ( search-condition , estimate )
|  search-condition IS [ NOT ] { TRUE | FALSE | UNKNOWN }
| trigger-operation
comparison-operator :
 =   
| >  
| <  
| >=  
| <=  
| <>  
| !=  
| !< 
| !>
trigger-operation :
INSERTING 
| DELETING
| UPDATING [ ( column-name-string ) ] 
| UPDATE( column-name )
Parameters
Remarks

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.

The LIKE, SIMILAR TO, and REGEXP search conditions are very similar. To understand similarities and differences between them, see LIKE, REGEXP, and SIMILAR TO search conditions.

Permissions

Must be connected to the database.

Side effects

None.

See also

Subqueries in search conditions
ALL search condition
ANY and SOME search conditions
BETWEEN search condition
LIKE, REGEXP, and SIMILAR TO search conditions
IN search condition
CONTAINS 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