MySQL 如何使用变量创建准备语句？

Question

这是我尝试使用的存储过程

DELIMITER ##
CREATE PROCEDURE exportFile()
BEGIN

DECLARE filename VARCHAR(255);

SET filename = CONCAT('~/Sample',NOW(),'.csv'));
SET @outfilestmt = concat('SELECT * INTO OUTFILE ',"'", filename,"'",' FROM Results') ;

PREPARE stmt FROM @outfilestmt;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

END ##
DELIMITER ;

这是我收到的错误

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 ');
SET @outfilestmt = concat('SELECT * INTO OUTFILE ',"'", filename,"'",' FROM R' at line 6

期望的结果:

call exportFile
--~/Sample2012-03-14-10:42:51.cvs

call exportFile
--~/Sample2012-03-14-10:42:52.cvs

call exportFile
--~/Sample2012-03-14-10:42:53.cvs

Answer 1

后面缺少分号

SET filename = CONCAT('~/Sample',NOW(),'.csv'))

而且一个大括号太多了(Devart 也指出了。谢谢)。将其更改为

SET filename = CONCAT('~/Sample',NOW(),'.csv');

测试了一下可以确定。有效!