Predicates
A predicate specifies a condition that is true,
false, or unknown about a given 
value,
row,
or group.
The following rules apply to all types of predicates:
- Predicates are evaluated after the expressions that are operands of the predicate.
- All values specified in the same predicate must be compatible.
- The value of a variable may be null (that is, the variable may have a negative indicator variable).
- The CCSID conversion of operands of predicates involving two or more operands are done according to Conversion rules for comparison:.
- Use of a DataLink value is limited to the NULL predicate.
Row-value expression: The operand of several predicates (basic, quantified, and IN) can be a row-value-expression:
A row-value-expression returns a single row that consists of one or more column values. The values can be specified as a list of expressions. The number of columns that are returned by the row-value-expression is equal to the number of expressions that are specified in the list.
- Basic predicate
A basic predicate compares two values or compares a set of values with another set of values. - Quantified predicate
A quantified predicate compares a value or values with a set of values. - BETWEEN predicate
The BETWEEN predicate compares a value with a range of values. - DISTINCT predicate
The DISTINCT predicate compares a value with another value. - EXISTS predicate
The EXISTS predicate tests for the existence of certain rows. - IN predicate
The IN predicate compares a value or values with a set of values. - LIKE predicate
The LIKE predicate searches for strings that have a certain pattern. The pattern is specified by a string in which the underscore and percent sign have special meanings. Trailing blanks in a pattern are a part of the pattern. - NULL predicate
The NULL predicate tests for null values. - REGEXP_LIKE predicate
The REGEXP_LIKE predicate searches for a regular expression pattern in a string. - Trigger event predicates
A trigger event predicate is used in a triggered action to test the event that activated the trigger. It is only allowed in the triggered action of a CREATE TRIGGER statement.
Parent topic: Language elements