表格Remark
包含如下所示的数据:
SerialNo | RemarkNo | Desp
=============================================
10 | 1 | rainy
10 | 2 | sunny
11 | 1 | sunny
11 | 2 | rainy
11 | 3 | cloudy
11 | 4 | sunny
12 | 1 | rainy
什么查询将返回以下结果:
10 | 1 | rainy
11 | 3 | cloudy
12 | null | null
也就是说,应该返回每组中的第二个最后一条记录?
假设SerialNo的所有RemarkNo都是连续的。备注数量越大,评论越晚。因此,序列号10的第二个RemarkNo是1,Desp'rainy'。
答案 0 :(得分:5)
尝试:
select s.SerialNo, r.RemarkNo, r.Desp
from (select SerialNo, max(RemarkNo) maxRemark from Remark group by SerialNo) s
left join Remark r on s.SerialNo = r.SerialNo and s.maxRemark-1 = r.RemarkNo
答案 1 :(得分:0)
这里有一些sql伪代码可以帮助你入门:
select
penultimate.*
from data as penultimate
left join (
/* query on data to return last row frome each group */
) as ultimate
on /* sql to join 2nd last record on each group to last group */
where not ultimate.SerialNo is null
答案 2 :(得分:0)
完全无效的解决方案,但有效...
SELECT
SerialNo,
RemarkNo,
(SELECT Desp
FROM Remarks
WHERE SerialNo = r3.SerialNo AND RemarkNo = r3.RemarkNo) Desp
FROM (
SELECT
r.SerialNo,
(SELECT r2.RemarkNo
FROM Remarks r2
WHERE r.SerialNo = r2.SerialNo
ORDER BY r2.RemarkNo DESC
LIMIT 1, 1) RemarkNo
FROM (SELECT DISTINCT SerialNo FROM Remarks) r) r3