如何在select语句中获取变量值

Question

SET Project_List_val=CONCAT(Project_Number_val,'_List'); 
Insert Into test (Manthan_Panel_Id) select Manthan_Panel_Id from Project_List_val where Project_Number_val='9'; 

在insert语句中，有一个名为'Project_List_val'的变量，它包含在上述步骤中进行了拼接的表名。这个语句没有将变量的内容作为表名取代，而是将'Project_List_val'作为表名并给出表未找到错误。

有什么建议吗？

Answer 1

默认情况下你不能参数表名和列名，所以你需要创建为动态SQL，

SET @Project_List_val = CONCAT(Project_Number_val, '_List'); 
SET @projNum = 9; 
SET @sql = CONCAT(' INSERT INTO test (Manthan_Panel_Id) 
        SELECT Manthan_Panel_Id 
        FROM ', @Project_List_val, ' 
        WHERE Project_Number_val = ?'); 

PREPARE stmt FROM @sql; 
EXECUTE stmt USING @projNum; 
DEALLOCATE PREPARE stmt;