Question

考虑一下这个sql：

SELECT DATE_FORMAT( Orders.Timestamp,  '%Y%m' ) AS Period,
SUM(Price) AS 'Ordersum per month and organisation', Orders.Organisation,
(
  SELECT SUM(Amount) AS Returns
  FROM Returns
  WHERE DATE_FORMAT( Returns.Timestamp,  '%Y%m' ) = Period
  AND Returns.Organisation = Orders.Organisation
) Returns
FROM Orders
GROUP BY Period, Organisation

每当子查询中的行在主查询中没有等效的句点时，就不会显示该行。原因是查询从订单表中获取其周期，并且当子查询的周期与订单表中的句点不匹配时，它根本不匹配查询。

有没有办法重新格式化此查询以实现我想要的目标？

Sqlfiddle http://sqlfiddle.com/#!9/ace715/1

Answer 1

您可以使用UNION左右连接，如下所示：

SELECT 
ifnull(DATE_FORMAT( Orders.Timestamp,'%Y%m' ),DATE_FORMAT(Returns.Timestamp,'%Y%m' )) AS Period,
SUM(Price) AS 'Ordersum per month and organisation',
ifnull(Orders.Organisation,Returns.Organisation) as 'Organisation',
SUM(Amount) AS 'Returns'
FROM Orders
left JOIN Returns 
on DATE_FORMAT( Orders.Timestamp,'%Y%m' ) = DATE_FORMAT(Returns.Timestamp,  '%Y%m' ) 
and Returns.Organisation = Orders.Organisation
GROUP BY Period, Returns.Organisation, Orders.Organisation
union
select ifnull(DATE_FORMAT( Orders.Timestamp,  '%Y%m' ),DATE_FORMAT(Returns.Timestamp,'%Y%m' )) AS Period,
SUM(Price) AS 'Ordersum per month and organisation',
ifnull(Orders.Organisation,Returns.Organisation),
SUM(Amount) AS 'Returns'
FROM Orders
right JOIN Returns 
on DATE_FORMAT( Orders.Timestamp,  '%Y%m' ) = DATE_FORMAT(Returns.Timestamp, '%Y%m' ) 
and Returns.Organisation = Orders.Organisation
GROUP BY Period, Returns.Organisation, Orders.Organisation

重新格式化sql以显示主查询返回null的行

1 个答案: