Boolean predicate

Retrieves rows where the value of an expression is true, false, or unknown (null).


expression IS [NOT] TRUE
expression IS [NOT] FALSE
expression IS [NOT] UNKNOWN


  • A null input is treated as the value UNKNOWN.
  • IS UNKNOWN and IS NOT UNKNOWN are effectively the same as the NULL predicate, except that the input expression does not have to be a single column value. To check a single column value for NULL, use the NULL-predicate.
  • Do not confuse the boolean-predicate with Boolean Operators or the Boolean data type, which can have only two values: true and false.