mysql - 动态列别名

Question

您好我有"SQL查询",看看在上周的每个成员这样做,我创建的"SQL查询",它是工作很会工作的数量,但我想从ALISE改变week1或week2到的这个数据本周我的"SQL查询"是:

SELECT `staffID`,  
 SUM(if (created_at BETWEEN NOW()-INTERVAL 1 WEEK AND NOW(), 1,0)) 
 AS `week1`, 
 SUM(if (created_at BETWEEN NOW()-INTERVAL 2 WEEK AND NOW()-INTERVAL 1 WEEK, 1,0)) 
 AS `week2`, 
FROM tasks 
WHERE status ='done'
GROUP BY `staffID

我想成为这样的"sql查询",但mysql给我错误.那么,无论如何要解决这个问题？

SELECT `staffID`,  
 SUM(if (created_at BETWEEN NOW()-INTERVAL 1 WEEK AND NOW(), 1,0)) 
 AS NOW()-INTERVAL 1 WEEK, 
 SUM(if (created_at BETWEEN NOW()-INTERVAL 2 WEEK AND NOW()-INTERVAL 1 WEEK, 1,0)) 
 AS NOW()-INTERVAL 2 WEEK, 
FROM tasks 
WHERE status ='done'
GROUP BY `staffID

sql给我这条消息:

1064 - 您的SQL语法出错; 查看与您的MySQL服务器版本对应的手册,以便在'NOW()附近使用正确的语法 - INTERVAL 1 WEEK

Answer 1

答案很简单:在SQL中不可能.列别名是常量.您必须动态创建查询以实现您想要的:

SET @column_alias1 := NOW() - INTERVAL 1 WEEK;
SET @column_alias2 := NOW() - INTERVAL 2 WEEK;
SET @query := CONCAT('SELECT SUM(...) AS `', @column_alias1, '`, SUM(...) AS `', @column_alias2, '` FROM ...');
PREPARE dynamic_statement FROM @query;
EXECUTE dynamic_statement;