Question

我有一个选择第n个结果的查询（在这种情况下是第10个）我只想使用第n个结果的reply_chunk_id并计算其他类似的结果来查看总共有多少个具有相同id的结果。有人知道如何在一个查询中执行此操作吗？

SELECT reply_chunk_id,message 
FROM (
    SELECT * 
    FROM messages
    ORDER BY timestamp ASC
    LIMIT 10
) AS tbl WHERE topic_id=?
ORDER BY timestamp DESC
LIMIT 1

Answer 1

您可以按

选择第10行

SELECT reply_chunk_id FROM messages ORDER BY timestamp ASC LIMIT 9,1

所以

SELECT COUNT(*) FROM messages
   WHERE reply_chunk_id = (SELECT reply_chunk_id FROM messages
                              ORDER BY timestamp ASC LIMIT 9,1)
     AND topic_id = ?

Answer 2

可能使用LIMIT 1 OFFSET 9。不确定这是在MySQL中构建的。

Answer 3

SELECT COUNT(1)
FROM messages
WHERE reply_chunk_id =
(SELECT MIN(reply_chunk_id)
 FROM messages
 WHERE timestamp =
    (SELECT MAX(timestamp)
     FROM   (SELECT timestamp
             FROM   messages
             ORDER BY timestamp ASC
             LIMIT 10)))

mysql计数选中的字段

3 个答案: