Stored Procedure Overview

存储过程通常通过CALL语句进行调用。它可以有输入参数、输出参数和既有输入也有输出的参数。

创建存储过程

下面是一个存储过程的简单示例：

DELIMITER //

CREATE PROCEDURE Reset_animal_count() 
 MODIFIES SQL DATA
 UPDATE animal_count SET animals = 0;
//

DELIMITER ;

首先，修改了系统默认的语句结束符（;）为（//）。这个过程被命名为Reset_animal_count。modified SQL DATA表示该过程将执行类似于写操作的操作，并修改数据。它仅用于咨询目的。最后，是实际的SQL语句——一个UPDATE语句。

SELECT * FROM animal_count;
+---------+
| animals |
+---------+
|     101 |
+---------+

CALL Reset_animal_count();

SELECT * FROM animal_count;
+---------+
| animals |
+---------+
|       0 |
+---------+

A more complex example, with input parameters, from an actual procedure used by banks:

CREATE PROCEDURE
  Withdraw                             /* Routine name */
  (parameter_amount DECIMAL(6,2),     /* Parameter list */
  parameter_teller_id INTEGER,
  parameter_customer_id INTEGER)
  MODIFIES SQL DATA                   /* Data access clause */
  BEGIN                        /* Routine body */
    UPDATE Customers
        SET balance = balance - parameter_amount
        WHERE customer_id = parameter_customer_id;
    UPDATE Tellers
        SET cash_on_hand = cash_on_hand + parameter_amount
        WHERE teller_id = parameter_teller_id;
    INSERT INTO Transactions VALUES (
        parameter_customer_id,
        parameter_teller_id,
        parameter_amount);
  END;

See CREATE PROCEDURE for full syntax details.

为什么使用存储过程?

Security is a key reason. Banks commonly use stored procedures so that applications and users don't have direct access to the tables. Stored procedures are also useful in an environment where multiple languages and clients are all used to perform the same operations.

Stored Procedure listings and definitions

To find which stored functions are running on the server, use SHOW PROCEDURE STATUS.

SHOW PROCEDURE STATUS\G
*************************** 1. row ***************************
                  Db: test
                Name: Reset_animal_count
                Type: PROCEDURE
             Definer: root@localhost
            Modified: 2013-06-03 08:55:03
             Created: 2013-06-03 08:55:03
       Security_type: DEFINER
             Comment: 
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

or query the routines table in the INFORMATION_SCHEMA database directly:

SELECT ROUTINE_NAME FROM INFORMATION_SCHEMA.ROUTINES 
  WHERE ROUTINE_TYPE='PROCEDURE';
+--------------------+
| ROUTINE_NAME       |
+--------------------+
| Reset_animal_count |
+--------------------+

To find out what the stored procedure does, use SHOW CREATE PROCEDURE.

SHOW CREATE PROCEDURE Reset_animal_count\G
*************************** 1. row ***************************
           Procedure: Reset_animal_count
            sql_mode: 
    Create Procedure: CREATE DEFINER=`root`@`localhost` PROCEDURE `Reset_animal_count`()
    MODIFIES SQL DATA
UPDATE animal_count SET animals = 0
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

删除和更新存储过程

To drop a stored procedure, use the DROP PROCEDURE statement.

DROP PROCEDURE Reset_animal_count();

To change the characteristics of a stored procedure, use ALTER PROCEDURE. However, you cannot change the parameters or body of a stored procedure using this statement; to make such changes, you must drop and re-create the procedure using CREATE OR REPLACE PROCEDURE (which retains existing privileges), or DROP PROCEDURE followed CREATE PROCEDURE .

存储过程的权限

See the article Stored Routine Privileges.