表中的mysql存储过程设置值 [英] mysql stored procedure set value from table

问题描述

我有一个简单的下表:

mysql> select * from version;
+----+---------+
| id | version |
+----+---------+
|  1 | 1       |
+----+---------+
1 row in set (0.00 sec)

我需要创建一个存储过程，该存储过程将根据此表的值(确切地说，该表的唯一行)执行某些操作(或不执行任何操作).

I need to create a stored procedure that will do something (or nothing) depending on the value of this table (precisely, the only row of this table).

DELIMITER $$
DROP PROCEDURE IF EXISTS upgrade_version $$
CREATE PROCEDURE upgrade_version(current_version INTEGER, script TEXT)
BEGIN
  DECLARE version INT(11);
  SET version = (SELECT `version` FROM `version` WHERE `id` = 1 LIMIT 1);
  SELECT version;
  IF version = current_version + 1 THEN
    PREPARE upgrade_stmt FROM script;
    EXECUTE upgrade_stmt;
    UPDATE `version` SET `version` = `version` + 1 WHERE `id` = 1;
  ENDIF;
END $$
DELIMITER ;

在以下位置被调用

CALL upgrade_version(1,'ALTER TABLE ...');

语法上不正确，mysql返回:

It is syntactically incorrect, mysql returns:

1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'script;
    EXECUTE upgrade_stmt;
    UPDATE `version` SET `version` = `version`' at line 7 

怎么了?

推荐答案

尝试一下:

DELIMITER $$
DROP PROCEDURE IF EXISTS upgrade_version $$
CREATE PROCEDURE upgrade_version(current_version INT, script TEXT)
BEGIN
  SELECT `version` into @ver FROM `version` WHERE `id` = 1 LIMIT 1;  
  SET @s = script;
  IF @ver = current_version + 1 THEN
    PREPARE upgrade_stmt FROM @s;
    EXECUTE upgrade_stmt;
    DEALLOCATE PREPARE upgrade_stmt;
    UPDATE `version` SET `version` = `version` + 1 WHERE `id` = 1;
  END IF;
END $$
DELIMITER ;

这篇关于表中的mysql存储过程设置值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！