Boolean-Predicate
Retrieves rows where the value of an expression is true, false, or unknown (null).
Syntax
expression IS [NOT] TRUE expression IS [NOT] FALSE expression IS [NOT] UNKNOWN
Notes
- A null input is treated as the value
UNKNOWN
. IS UNKNOWN
andIS 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 forNULL
, 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.