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
IS NOT UNKNOWNare 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.