The Boolean operators AND, OR and NOT allow combining multiple search conditions to complex Boolean expressions.
The result of the Boolean operations is given in the following tables:
AND |
TRUE |
FALSE |
unknown |
---|---|---|---|
TRUE |
TRUE |
FALSE |
unknown |
FALSE |
FALSE |
FALSE |
FALSE |
unknown |
unknown |
FALSE |
unknown |
OR |
TRUE |
FALSE |
unknown |
---|---|---|---|
TRUE |
TRUE |
TRUE |
TRUE |
FALSE |
TRUE |
FALSE |
unknown |
unknown |
TRUE |
unknown |
unknown |
NOT |
TRUE |
FALSE |
unknown |
---|---|---|---|
FALSE |
TRUE |
unknown |
<boolean expression> ::= <boolean term> | <search condition> OR <boolean term>. <boolean term> ::= <boolean factor> | <boolean term> AND <boolean factor>. <boolean factor> ::= ( NOT )? ( <predicate> | '(' <search condition> ')' ).
Example
SELECT * FROM employees WHERE employee_name LIKE 'John%' OR NOT ( salary > 50000 AND employee_name = 'Mary Jones')
Boolean Operations. The query selects all employees with a name starting with 'John' or with a salary not exceeding 50000 or with a name equal to 'Mary Jones'.
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