mysql - mysql stored procedure set value from table

Question

I've got a following, simple table:

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

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 ;

To be called within:

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

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 

What is wrong?

Answer 1

我不明白您为什么选择“SELECT 版本”，如果您想选择必须将其检索到变量中的数据，那么当您直接在终端上使用它时，该语句可以正常工作。你确定你的脚本中有prepared_stmt ..！？可能的解决方法是：

1. 将变量名 version 更改为 version_v

2. 而不是这个：

   SET 版本 = (SELECT versionFROM versionWHERE id= 1 LIMIT 1);
   选择版本；

尝试这个：

SELECT `version` INTO Version_v FROM `version` WHERE `id` = 1 LIMIT 1);

Answer 2

尝试这个：

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 ;

Answer 3

设置值以声明变量

       DELIMITER $$
       create procedure Testing()
           begin
            declare Regione int;   
            set Regione=(select  id from users
            where id=1) ;
            select Regione ;
           end $$
         DELIMITER;