无法在 Union 查询中使用 order by

Question

我有以下原始 mysql 查询

select *, r.ReviewId AS ActualReviewId, r.DateCreated AS ActualDateCreated from review r LEFT join reviewphoto rp ON r.ReviewId = rp.ReviewId where r.DishId = ?
      UNION
      select *, r.ReviewId  AS ActualReviewId, r.DateCreated AS ActualDateCreated from review r RIGHT join reviewphoto rp ON r.ReviewId = rp.ReviewId where r.DishId = ?

我正在尝试添加排序依据，以便我可以按日期对数据进行排序，但出现以下错误

#1250 - Table 'rp' from one of the SELECTs cannot be used in ORDER clause

下面是修改后的查询：

(select *, r.ReviewId AS ActualReviewId, r.DateCreated AS ActualDateCreated from review r LEFT join reviewphoto rp ON r.ReviewId = rp.ReviewId where r.DishId = 46)
      UNION
      (select *, r.ReviewId  AS ActualReviewId, r.DateCreated AS ActualDateCreated from review r RIGHT join reviewphoto rp ON r.ReviewId = rp.ReviewId where r.DishId = 46) order by rp.DateCreated desc

Answer 1

如果您从 ORDER BY 子句中删除别名，您的最后一个查询应该有效：

(SELECT *, r.ReviewId AS ActualReviewId, r.DateCreated AS ActualDateCreated
 FROM review r
 LEFT JOIN reviewphoto rp ON r.ReviewId = rp.ReviewId
 WHERE r.DishId = 46)
 UNION
(SELECT *, r.ReviewId, r.DateCreated
 FROM review r
 RIGHT JOIN reviewphoto rp ON r.ReviewId = rp.ReviewId
 WHERE r.DishId = 46)
ORDER BY ActualDateCreated DESC;

无法在 Union 查询中使用 order by

Not able to use order by in Union query

mysql

union