mysql

创建数据表 runoob_test_tbl

root@host# mysql -u root -p password;

Enter password:*******

mysql> use RUNOOB;

Database changed

mysql> create table runoob_test_tbl

    -> (

    -> runoob_author varchar(40) NOT NULL,

    -> runoob_count  INT

    -> );

Query OK, 0 rows affected (0.05 sec)

mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('RUNOOB', 20);

mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('菜鸟教程', NULL);

mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('Google', NULL);

mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('FK', 20);

mysql> SELECT * from runoob_test_tbl;

+---------------+--------------+

| runoob_author | runoob_count |

+---------------+--------------+

| RUNOOB        | 20          |

| 菜鸟教程  | NULL        |

| Google        | NULL        |

| FK            | 20          |

+---------------+--------------+

4 rows in set (0.01 sec)

以下实例中你可以看到 = 和 != 运算符是不起作用的：

mysql> SELECT * FROM