php - 如何按列对分组元素内部进行排序？

Question

尝试订购此:

|    id    |    title    |    created_at    |

 1                            12:00  
 2                            13:00
 1                            15:00
 2                            15:00
 1                            17:00
 3                            18:00
 1                            19:00
 3                            20:00

进入此:

3    20:00
3    18:00
1    19:00
1    17:00
1    15:00
1    12:00
2    15:00
2    13:00

这段代码完成了对 id 进行分组的工作:

select t.*
from table t join
     (select t.id, max(created_at) as maxca
      from table t
      group by t.id
     ) tt
     on t.id = tt.id
order by tt.maxca desc, id;

问题在于created_at以相反的顺序出现，如下所示:

3    18:00
3    20:00
1    12:00
1    15:00
1    18:00
1    19:00
2    13:00
2    15:00

如何反转每个分组 id block 内的created_at顺序？

Answer 1

只需向 order by 添加另一个键即可:

select t.*
from table t join
     (select t.id, max(created_at) as maxca
      from table t
      group by t.id
     ) tt
     on t.id = tt.id
order by tt.maxca desc, id, created_at desc;