我在MySQL表tbl_test中有数据：
create table `tbl_test` (
`id` INT(10) NOT NULL UNIQUE,
`value` char(30),
`time` timestamp,
`id1` int(10)
);
INSERT INTO
`tbl_test` (`id`,`value`,`time`,`id1`)
VALUES
('3638','value1','2014-11-16 02:01:48','1'),
('3639','value2','2014-11-14 13:00:45','1'),
('3642','value3','2014-11-14 13:00:40','1'),
('3769','value4','2014-11-15 22:21:50','2'),
('3770','value5','2014-11-15 22:21:55','2'),
('3789','value6','2014-11-14 16:08:20','2'),
('3870','value7','2014-11-16 02:01:49','1');
所需结果（每id1行2行，如order by time desc limit 2每行{/ p>}：
+------+--------+---------------------+----+
| id | value | time |id1 |
+------+--------+---------------------+----+
| 3769 | value4 | 2014-11-15 22:21:50 | 2 |
| 3770 | value5 | 2014-11-15 22:21:55 | 2 |
| 3638 | value1 | 2014-11-16 02:01:48 | 1 |
| 3870 | value7 | 2014-11-16 02:01:49 | 1 |
+------+--------+---------------------+----+
我的查询最接近：
select * from (
select max(id) as id from tbl_test group by id1
union all
select max(id) from tbl_test tmp1
where id not in (SELECT max(id) from tbl_test tmp2 where tmp1.id1 = tmp2.id1)
group by id1
) as tmp
left join tbl_test USING(id);
+------+--------+---------------------+----+
| id | value | time |id1 |
+------+--------+---------------------+----+
| 3770 | value5 | 2014-11-15 22:21:55 | 2 |
| 3789 | value6 | 2014-11-14 16:08:20 | 2 |
| 3642 | value3 | 2014-11-14 13:00:40 | 1 |
| 3870 | value7 | 2014-11-16 02:01:49 | 1 |
+------+--------+---------------------+----+
但我对max(id)有疑问。表是网格化的，我需要时间desc限制2。
答案 0 :(得分：1)
我认为这就是你要找的东西：
＆＃34;对于每个id1，返回最新time（最大id为决胜局）的两行＆＃34; ：< / p>
使用标准SQL 窗口函数，这很简单：
SELECT id, value, time, id1
FROM (
SELECT t.*
, row_number() OVER (PARTITION BY id1 ORDER BY time DESC, id DESC) AS rn
FROM tbl_test t
) sub
WHERE rn < 3
ORDER BY id1 DESC, time DESC, id DESC;
但 MySQL 不提供窗口功能。您可以使用用户定义的变量替换：
SELECT id, value, time, id1
FROM (
SELECT t.*
, @rn := CASE WHEN @prev = id1 THEN @rn + 1 ELSE 1 END rn
, @prev := id1
FROM tbl_test t
, (SELECT @rn := 0) r
ORDER BY id1 DESC, time DESC, id DESC
) sub
WHERE rn < 3
ORDER BY id1 DESC, time DESC, id DESC;
相关问题：
答案 1 :(得分：0)
似乎您希望每个id1的行具有最近的时间。
select t.*
from tbl_test t join
(select id1, max(time) as maxtime
from tbl_test
group by id1
) tt
on t.id1 = tt.id1 and t.time = tt.maxtime
order by time;