SQL查询以获取另一列中每个唯一值的最大值

Question

ID  Sum Name
a   10  Joe
a   8   Mary
b   21  Kate
b   110 Casey
b   67  Pierce

What would you recommend as the best way to obtain for each ID the name that corresponds to the largest sum (grouping by ID). What I tried so far:

select ID, SUM(Sum) s, Name
from Table1
group by ID, Name
Order by SUM(Sum) DESC;

this will arrange the records into groups that have the highest sum first. Then I have to somehow flag those records and keep only those. Any tips or pointers? Thanks a lot

In the end I'd like to obtain:

a 10 Joe
b 110 Casey

Answer 1

You want the row_number() function:

select id, [sum], name
from (select t.*]
             row_number() over (partition by id order by [sum] desc) as seqnum
      from table1
     ) t
where seqnum = 1;

Your question is more confusing than it needs to be because you have a column called sum . You should avoid using SQL reserved words for identifiers.

The row_number() function assigns a sequential number to a group of rows, starting with 1. The group is defined by the partition by clause. In this case, all rows with the same id are in the same group. The ordering of the numbers is determined by the order by clause, so the one with the largest value of sum gets the value of 1 .

If you might have duplicate maximum values and you want all of them, use the related function rank() or dense_rank() .

Answer 2

select * 
from
 (
   select *
    ,rn = row_number() over (partition by Id order by sum desc)
   from table
 )x
where x.rn=1

demo