Boolean Data Type

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.