mysql - 动态列别名

Question

嗨，我有＆＃34; sql查询＆＃34;查看上周每个成员完成的工作数量，以便我创建＆＃34; sql查询＆＃34;并且它的工作非常有意义，但我想将 week1或week2 更改为本周的数据我的＆＃34; sql查询＆＃34;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＆＃34; sql查询＆＃34;，但mysql给我错误。那么，无论如何都要解决这个问题吗？

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目标：

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;

Answer 2

检查它是否有效。

为列名添加了括号。

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