mysql - 如何执行存储在 MySQL 表列中的查询？

Question

mysql> select * from CT;

| CID | MID | REPORT_QUERY           |
|   1 |   1 | select * from emp;     |
|   2 |   2 | select * from student; |

2 rows in set (0.00 sec)

我想在 REPORT_QUERY 列中执行查询。

DELIMITER //
 CREATE PROCEDURE TRYct()
   BEGIN
SET @str=(SELECT GROUP_CONCAT(REPORT_QUERY SEPARATOR ' ') FROM CT);
PREPARE q from @str;
EXECUTE q;
   END //
 DELIMITER ;

我使用这段代码，但如果我的表中只有一个查询，它就可以工作。如果有两个查询比它给出一个错误。

ERROR 1064 (42000): 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 'select * from student' at line 1

问题出在哪里？帮助我。

Answer 1

您可以使用游标获取CT 表上的每个REPORT_QUERY，并使用准备好的语句执行:

delimiter $$
drop procedure if exists run_queries$$
create procedure run_queries()
begin

    declare s_query varchar(255);

    declare done bool default false;
    declare c_queries cursor for    
        select REPORT_QUERY from CT;
    declare continue handler for not found set done = true;


    open c_queries;
    read_loop: loop

        fetch c_queries into s_query;
        if done then 
            leave read_loop;
        end if;

        -- run the query
        set @sql = s_query;
        prepare stmt from  @sql;
        execute stmt;
        deallocate prepare stmt;
    end loop;

end$$

创建过程后，您可以调用如下:

调用 run_queries();

就是这样。