Select multiple (non-aggregate function) columns with GROUP BY

Question

I am trying to select the max value from one column, while grouping by another non-unique id column which has multiple duplicate values. The original database looks somethin

Answer 1

You have yourself a greatest-n-per-group problem. This is one of the possible solutions:

select c.mukey, c.comppct_r, c.name, c.type
from c yt
inner join(
    select c.mukey, max(c.comppct_r) comppct_r
    from c
    group by c.mukey
) ss on c.mukey = ss.mukey and c.comppct_r= ss.comppct_r

Another possible approach, same output:

select c1.*
from c c1
left outer join c c2
on (c1.mukey = c2.mukey and c1.comppct_r < c2.comppct_r)
where c2.mukey is null;

There's a comprehensive and explanatory answer on the topic here: SQL Select only rows with Max Value on a Column