BOOLEAN
BOOLEAN
The SQL-compliant BOOLEAN
data type (8 bits) comprises the distinct truth values TRUE
and FALSE
.Unless prohibited by a NOT NULL
constraint, the BOOLEAN
data type also supports the truth value UNKNOWN
as the null value.The specification does not make a distinction between the NULL
value of this data type, and the truth value UNKNOWN
that is the result of an SQL predicate, search condition, or Boolean value expression: they may be used interchangeably to mean the same thing.
As with many programming languages, the SQL BOOLEAN
values can be tested with implicit truth values.For example, field1 OR field2
and NOT field1
are valid expressions.