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Boolean predicate

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A Boolean predicate returns the truth value of a Boolean expression.

Read syntax diagramSkip visual syntax diagram boolean-expression ISTRUEISNOTTRUEFALSE
boolean-expression
An expression that returns a built-in Boolean, character string, graphic string, integer, or decimal floating-point data type. A character string, graphic string, integer, or decimal floating-point value is cast to Boolean. For more information about converting character string, graphic string, integer, and decimal floating-point to Boolean, see BOOLEAN.
Null values are treated differently by different predicates:
  • The IS TRUE predicate returns:
    • TRUE when the truth value of the value returned by boolean-expression is TRUE
    • FALSE when the truth value is FALSE or NULL
  • The IS FALSE predicate returns:
    • TRUE when the truth value of the value returned by boolean-expression is FALSE
    • FALSE when the truth value is TRUE or NULL
  • The IS NOT TRUE predicate returns:
    • TRUE when the truth value of the value returned by boolean-expression is FALSE or NULL
    • FALSE when the truth value is TRUE
  • The IS NOT FALSE predicate returns:
    • TRUE when the truth value of the value returned by boolean-expression is TRUE or NULL
    • FALSE when the truth value is FALSE

Alternative syntax: The keyword ON can be used instead of TRUE; OFF can be used instead of FALSE.

Example

The following statement returns the rows from TB1 that have not had the Boolean column SHIPPED set to TRUE.

  SELECT * FROM TB1 WHERE SHIPPED IS NOT TRUE
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