Question

正如标题所述，我想从每个月中选择一个具有最新日期的记录。我有一张这样的桌子：

ID  field1          field2          created_at
----------------------------------------------
1   40000.0000      70000.0000      2018-01-31
2   80000.0000      90000.0000      2018-02-28
3   10000.0000      30000.0000      2018-03-31
4   12000.0000      32000.0000      2018-04-30
5   212500.0000     312500.0000     2018-05-31
6   324000.0000     424000.0000     2018-06-30
7   122300.0000     222300.0000     2018-07-26
8   357772.2420     307600.9081     2018-07-31

我提出了这个查询，但是它没有按预期工作。

SELECT id，field1，field2，MAX（created_at）AS created_at来自my_table GROUP BY YEAR（created_at），MONTH（created_at）ORDER BY created_at ASC

我得到的输出：

ID  field1          field2          created_at
----------------------------------------------
1   40000.0000      70000.0000      2018-01-31
2   80000.0000      90000.0000      2018-02-28
3   10000.0000      30000.0000      2018-03-31
4   12000.0000      32000.0000      2018-04-30
5   212500.0000     312500.0000     2018-05-31
6   324000.0000     424000.0000     2018-06-30
7   122300.0000     222300.0000     2018-07-31   <-- values from ID 7 but date from ID 8

预期产量

ID  field1          field2          created_at
----------------------------------------------
1   40000.0000      70000.0000      2018-01-31
2   80000.0000      90000.0000      2018-02-28
3   10000.0000      30000.0000      2018-03-31
4   12000.0000      32000.0000      2018-04-30
5   212500.0000     312500.0000     2018-05-31
6   324000.0000     424000.0000     2018-06-30
8   357772.2420     307600.9081     2018-07-31

如何从与MAX(created_at)相同的记录中选择值？

SQLFiddle

Answer 1

您可以尝试以下方法：

SELECT id, field1, field2, created_at AS created_at 
FROM `my_values` 
where created_at in (select max(created_at)
                 FROM `my_values` 
 GROUP BY YEAR(created_at), MONTH(created_at) ORDER BY created_at ASC )

See SQLFiddle

Answer 2

通过加入

select id, field1, field2,T2.created_at from my_values T1 
inner join 
(
select max(created_at) as created_at
                 FROM `my_values` 
 GROUP BY YEAR(created_at), MONTH(created_at) ORDER BY created_at ASC
 ) as T2
 on T1.created_at=T2.created_at

http://sqlfiddle.com/#!9/4f7442/18

id  field1  field2  created_at
1   40000   70000   2018-01-31
2   80000   90000   2018-02-28
3   10000   30000   2018-03-31
4   12000   32000   2018-04-30
5   212500  312500  2018-05-31
6   324000  424000  2018-06-30
8   357772.242  307600.9081 2018-07-31

如何获得每个月的最后日期

2 个答案: