如何根据条件从sql表中记录信息

Question

在下表中记录玩家信息（玩家信息）。检查每个玩家的最高级别（玩家ID）和该级别下的最小差距。

 player_id   level   gap
    -----------------------
    123         8       20
    123         9       40
    123         9       30
    246         [NULL]  10
    246         6       30
    246         6       20
    ----------------------- 

Answer 1

在Postgres中，您将使用distinct on：

select distinct on (player_id), t.*
from t
order by player_id, level desc, gap;

在MySQL或Postgres中，您可以执行：

select t.*
from (select t.*,
             row_number(player_id) order by (level desc, gap) as seqnum
      from t
     ) t
where seqnum = 1;

Answer 2

这里查询，您可以为此使用min()和max()函数。

select min(t1.gap), t2.lev, t1.player_id
from tableA t1
inner join 
    (select max(lev) lev, player_id
    from tableA
    group by player_id) t2 on t2.lev=t1.lev and t1.player_id = t2.player_id
group by t1.player_id, t2.lev

请参见dbfiddle。