在mysql中传递变量时出错

Question

我一直在每个简单的Mysql查询中花费数小时（搜索和尝试）。我试图从一个select语句传递一个变量到下一个语句。但是我已经抛出了空行。

SET @id :='SELECT MAX(sId) from surveys'; 
SELECT typeId as type from surveys WHERE [email protected]; 
PREPARE stmt from @id; 
execute stmt; 

我试着执行SELECT MAX(sId) from surveys，它给出了所需的结果。但似乎@id不接受这些值。有没有任何错误或任何其他建议来解决这个问题？

Answer 1

试试这个：

SET @s = 'SELECT typeId as type from surveys WHERE sId=?'; 
PREPARE stmt from @s; 
SET @id = (SELECT MAX(sId) from surveys); 
EXECUTE stmt USING @id; 

DEALLOCATE PREPARE stmt;