获取SELECT语句中的最后3行，并将其设为ASC顺序

Question

我有一个mysql查询，我只想查询SELECT语句的最后3行，我想再次将我的查询重新排序为ASC顺序，因为子查询在DESC中。

 SELECT * FROM( 
      SELECT * 
      FROM post_replies 
      WHERE post_replies.post_hash=:posthash 
      ORDER BY post_replies.reply_id DESC 
      LIMIT 3)
    ORDER BY reply_id ASC

这就是出现的错误

我不明白我怎么能把mysql别名在这里定义在这里

如何使查询只获取select语句的最后3行，并按ASC顺序生成结果？

Answer 1

我不是MySQL专家，但别名会跟在派生表后面，如下所示：

SELECT * FROM( 
  SELECT * 
  FROM post_replies 
  WHERE post_replies.post_hash=:posthash 
  ORDER BY post_replies.reply_id DESC 
  LIMIT 3) ---> AS MyDerivedTable <---
ORDER BY reply_id ASC

Answer 2

错误只是告诉您需要调用subselect。将别名放在子选择后的右括号后。这应该是有效的：

 SELECT a.* FROM( 
      SELECT * 
      FROM post_replies 
      WHERE post_replies.post_hash=:posthash 
      ORDER BY post_replies.reply_id DESC 
      LIMIT 3) a
    ORDER BY a.reply_id ASC