IS NULL 조건식

설명

IS NULL 조건식은 왼쪽에 지정된 표현식의 결과가 NULL인지 비교하여, NULL인 경우 TRUE를 반환하며, 조건절 내에서 사용할 수 있다. NULL 키워드 앞에 NOT이 있으면 IS NULL 연산의 결과에 NOT 연산을 수행하여 결과를 반환한다.

구문

expression IS [ NOT ] NULL

예제

--selecting rows where salary is NULL

SELECT * FROM condition_tbl WHERE salary IS NULL;

 

=== <Result of SELECT Command in Line 1> ===

 

           id  name                  dept_name                  salary

======================================================================

            7  'Brown     '          'account'                    NULL

 

--selecting rows where salary is NOT NULL

SELECT * FROM condition_tbl WHERE salary IS NOT NULL;

 

=== <Result of SELECT Command in Line 1> ===

 

           id  name                  dept_name                  salary

======================================================================

            1  'Kim       '          'devel'                   4000000

            2  'Moy       '          'sales'                   3000000

            3  'Jones     '          'sales'                   5400000

            4  'Smith     '          'devel'                   5500000

            5  'Kim       '          'account'                 3800000

            6  'Smith     '          'devel'                   2400000

 

--simple conparison operation returns NULL when operand is NULL

SELECT * FROM condition_tbl WHERE salary = NULL;

 

=== <Result of SELECT Command in Line 1> ===

 

There are no results.

 

0 rows selected.