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。