MySQL管理与优化(9)：存储过程和函数

存储过程和函数

• 存储过程和函数是事先经过编译并存储在数据库中的一段SQL语句的集合。

存储过程或函数的相关操作

创建，修改存储过程或函数

• 相关语法

CREATE
    [DEFINER = { user | CURRENT_USER }]
    PROCEDURE sp_name ([proc_parameter[,...]])
    [characteristic ...] routine_body

CREATE
    [DEFINER = { user | CURRENT_USER }]
    FUNCTION sp_name ([func_parameter[,...]])
    RETURNS type
    [characteristic ...] routine_body

proc_parameter:
    [ IN | OUT | INOUT ] param_name type

func_parameter:
    param_name type

type:
    Any valid MySQL data type

characteristic:
    COMMENT 'string'
  | LANGUAGE SQL
  | [NOT] DETERMINISTIC
  | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }

routine_body:
    Valid SQL routine statement

• 范例

DELIMITER //

-- 创建存储过程
mysql> CREATE PROCEDURE cityname_by_id(IN cid INT, OUT total INT)
    -> READS SQL DATA
    -> BEGIN
    ->  SELECT id, city FROM city WHERE id=cid;
    ->
    ->  SELECT FOUND_ROWS() INTO total;
    -> END //
Query OK, 0 rows affected (0.06 sec)

-- 调用存储过程
mysql> CALL cityname_by_id(2, @res);
+----+----------+
| id | city     |
+----+----------+
|  2 | NeiJiang |
+----+----------+
1 row in set (0.00 sec)

Query OK, 1 row affected (0.01 sec)

mysql> SELECT @res;
+------+
| @res |
+------+
|    1 |
+------+
1 row in set (0.00 sec)

删除存储过程或函数

DROP {PROCEDURE | FUNCTION} [IF EXISTS] sp_name

查询存储过程或函数

mysql> SHOW PROCEDURE status like 'cityname_by_id'\G
*************************** 1. row ***************************
                  Db: mysqltest
                Name: cityname_by_id
                Type: PROCEDURE
             Definer: root@localhost
            Modified: 2014-06-17 15:22:11
             Created: 2014-06-17 15:22:11
       Security_type: DEFINER
             Comment:
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: utf8_general_ci
1 row in set (0.01 sec)

-- 查看存储过程或函数的定义
mysql> SHOW CREATE PROCEDURE cityname_by_id\G
*************************** 1. row ***************************
Procedure: cityname_by_id
sql_mode: STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
Create Procedure: CREATE DEFINER=`root`@`localhost` PROCEDURE `cityname_by_id`(IN cid INT, OUT total INT)
    READS SQL DATA
    BEGIN
        SELECT id, city FROM city WHERE id=cid;

        SELECT FOUND_ROWS() INTO total;
    END
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: utf8_general_ci
1 row in set (0.00 sec)

或者通过系统表information_schema.routines来查询：

mysql> SELECT * FROM information_schema.routines WHERE ROUTINE_NAME='cityname_by_id'\G

变量的使用

• 变量的定义：仅在BEGIN...END块中，语法为：

DECLARE var_name[,...] type [DEFAULT_VALUE]

DECLARE last_month_start DATE;

• 变量的赋值：可以直接赋值或查询赋值

SET var_name = expr [, var_name = expr] ...

# 表达式赋值
SET last_month_start = DATE_SUB(CURRENT_DATE(), INTERVAL 1 MONTH)

# SELECT INTO
SELECT .. FROM .. INTO var_name

• 定义条件和处理

-- 条件的定义
DECLARE condition_name CONDITION FOR condition_value
 
condition_value:
    SQLSTATE [VALUE] 
    sqlstate_value| 
    mysql_error_code

-- 条件的处理
DECLARE handler_type HANDLER FOR condition_value[, ...] sp_statement

handler_type:
     CONTINUE | EXIT | UNDO
condition_value:
    SQLSTATE [VALUE] 
    condition_name| 
    SQLWARNING | NOT FOUND | SQLEXCEPTION | mysql_error_code

范例：

-- 创建存储过程
mysql> CREATE PROCEDURE city_insert()
    -> BEGIN
    ->  INSERT INTO city VALUES (200, 'Beijing');
    ->  INSERT INTO city VALUES (200, 'Beijing');
    -> END;
    -> //
Query OK, 0 rows affected (0.00 sec)
-- 调用存储过程，第二句时报错
mysql> CALL city_insert()//
ERROR 1062 (23000): Duplicate entry '200' for key 'PRIMARY'

-- 修改存储过程，支持异常处理
DROP PROCEDURE IF EXISTS city_insert
mysql> CREATE PROCEDURE city_insert()
    -> BEGIN
    ->  DECLARE CONTINUE HANDLER FOR SQLSTATE '23000' SET @x = 1;
    ->  INSERT INTO city VALUES (300, 'ShangHai');
    ->  INSERT INTO city VALUES (300, 'ShangHai');
    -> END;
    -> //
Query OK, 0 rows affected (0.00 sec)

-- 再次调用，将不会抛出错误
mysql> CALL city_insert()//
Query OK, 0 rows affected, 1 warning (0.09 sec)

光标的使用

• 在存储过程和函数中可以使用光标对结果集进行循环的处理。

-- 声明光标
DECLARE cursor_name CURSOR FOR select_statement

-- OPEN 光标
OPEN cursor_name

-- FETCH 光标
FETCH cursor_name INTO var_name [, var_name]

-- CLOSE 光标
CLOSE cursor_name

• 范例

-- 定义存储过程
mysql> CREATE PROCEDURE city_stat()
    -> BEGIN
    ->  DECLARE cid INT;
    ->  DECLARE cname VARCHAR(20);
    ->  DECLARE cur_city CURSOR FOR SELECT * FROM city;
    ->  DECLARE EXIT HANDLER FOR NOT FOUND CLOSE cur_city;
    ->
    ->  SET @x1 = 0;
    ->  SET @x2 = 0;
    ->
    ->  OPEN cur_city;
    ->
    ->  REPEAT
    ->          FETCH cur_city INTO cid, cname;
    ->          IF cid <= 4 THEN
    ->                  SET @x1 = @x1 + cid;
    ->          ELSE
    ->                  SET @x2 = @x2 + cid * 2;
    ->          END IF;
    ->  UNTIL 0 END REPEAT;
    ->
    ->  CLOSE cur_city;
    ->
    -> END;
    -> //
Query OK, 0 rows affected (0.06 sec)

-- 执行存储过程
mysql> SELECT * FROM city;
+-----+----------+
| id  | city     |
+-----+----------+
|   2 | NeiJiang |
|   3 | HangZhou |
|  10 | ChengDu  |
| 200 | Beijing  |
| 300 | ShangHai |
+-----+----------+
5 rows in set (0.00 sec)

mysql> CALL city_stat();
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> SELECT @x1, @x2;
+------+------+
| @x1  | @x2  |
+------+------+
|    5 | 1020 |
+------+------+
1 row in set (0.00 sec)

• 变量，条件，处理程序，光标的声明是有顺序的，变量和条件必须在最前面声明，然后是光标的声明，最后是处理程序的生命。

流程控制

• 具体流程控制语句有：IF, CASE, LOOP, LEAVE, ITERATE, REPEAT, WHILE。
• 它们具体的用法可参考：http://dev.mysql.com/doc/refman/5.7/en/flow-control-statements.html

具体相关的细节可参考：

http://dev.mysql.com/doc/refman/5.7/en/create-procedure.html

不吝指正。