mysql这就是函数

之前学过存储 这就是存储.，函数与存储的区别就是函数必须返回一个值 。

函数创建

mysql> CREATE FUNCTION test(sex VARCHAR(20) ) RETURNS INT
    -> BEGIN
    -> DECLARE c INT ;
    -> SELECT COUNT(*) INTO c FROM student WHERE s_sex = sex;
    -> RETURN c ;
    -> END $
Query OK, 0 rows affected (0.03 sec)

函数调用

mysql> SELECT test('M')$
+-----------+
| test('M') |
+-----------+
|         3 |
+-----------+
1 row in set (0.01 sec)

函数查看

mysql> SHOW CREATE FUNCTION test
    -> $
+----------+--------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+
| Function | sql_mode                                   | Create Function                                                                                                                                                                 | character_set_client | collation_connection | Database Collation |
+----------+--------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+
| test     | STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION | CREATE DEFINER=`root`@`localhost` FUNCTION `test`(sex VARCHAR(20) ) RETURNS int(11)
BEGIN
DECLARE c INT ;
SELECT COUNT(*) INTO c FROM student WHERE s_sex = sex;
RETURN c ;
END | gbk                  | gbk_chinese_ci       | utf8mb4_0900_ai_ci |
+----------+--------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+--------------------+
1 row in set (0.00 sec)

函数删除

mysql> DROP FUNCTION test$
Query OK, 0 rows affected (0.04 sec)