SQL Reference Guide > SQL Reference Guide > Understanding the Elements of SQL Statements > Predicates in SQL > IS TRUE, IS FALSE, IS UNKNOWN Predicates
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IS TRUE, IS FALSE, IS UNKNOWN Predicates
The IS Boolean operator behaves according to the following truth table:
IS
TRUE
FALSE
UNKNOWN
True
True
False
False
False
False
True
False
Unknown
False
False
True
That is:
• IS TRUE is true for a BOOLEAN TRUE.
• IS FALSE is true for a BOOLEAN FALSE.
• IS UNKNOWN is true for an unknown (NULL) value.
• Every other comparison is false.
When applied to row value expressions, all elements must test the same.
Last modified date: 11/09/2022