IS NULL and = NULL : IS NULL « Query « SQL Server / T-SQL Tutorial

1. SQL Server / T-SQL Tutorial
2. Query
3. IS NULL

4>
5> CREATE TABLE titleauthor(
6>    au_id          varchar(20),
7>    title_id       varchar(20),
8>    au_ord         tinyint               NULL,
9>    royaltyper     int                   NULL
10> )
11> GO
1>
2> insert titleauthor values(null, '2', 1, 60)
3> insert titleauthor values('2', '3', 1, 100)
4> insert titleauthor values('3', '4', 1, 100)
5> insert titleauthor values('4', '5', 1, 100)
6> insert titleauthor values('5', '6', 1, 100)
7> insert titleauthor values('6', '7', 2, 40)
8> insert titleauthor values('7', '8', 1, 100)
9> insert titleauthor values('8', '9', 1, 100)
10> GO

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)
1>
2> select * from titleauthor where au_id is null;
3> GO
au_id                title_id             au_ord royaltyper
-------------------- -------------------- ------ -----------
NULL                 2                         1          60

(1 rows affected)
1> select * from titleauthor where au_id = null;
2> GO
au_id                title_id             au_ord royaltyper
-------------------- -------------------- ------ -----------

(0 rows affected)