Boolean Expressions

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'.

More Information

Search Condition