存储函数和存储过程 ​

CREATE FUNCTION 存储函数名称([参数列表])
RETURNS 返回值类型
BEGIN
    函数体内容
END

mysql> delimiter $
mysql> CREATE FUNCTION avg_score(s VARCHAR(100))
    -> RETURNS DOUBLE
    -> BEGIN
    ->     RETURN (SELECT AVG(score) FROM student_score WHERE subject = s);
    -> END $
Query OK, 0 rows affected (0.00 sec)

mysql> delimiter ;

mysql> SELECT avg_score('母猪的产后护理');
+------------------------------------+
| avg_score('母猪的产后护理')        |
+------------------------------------+
|                                 73 |
+------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT avg_score('论萨达姆的战争准备');
+------------------------------------------+
| avg_score('论萨达姆的战争准备')          |
+------------------------------------------+
|                                    73.25 |
+------------------------------------------+
1 row in set (0.00 sec)

mysql>

SHOW FUNCTION STATUS [LIKE 需要匹配的函数名]

SHOW CREATE FUNCTION 函数名

DROP FUNCTION 函数名