Question

I have a table that looks like this:

col1   col2  col3  
------ ----- ----- 
A      1     trout
A      2     trout
B      1     bass
C      1     carp
C      2     tuna
D      1     salmon

I really only want to select the rows with the max value for col2.

The query I want to generate would return the following:

col1   col2  col3  
------ ----- ----- 
A      2     trout
B      1     bass
C      2     tuna
D      1     salmon

I’ve tried something like this:

select col1, max (col2) as mCol2, col3
from mytable
group by col1, col2

In this case I get:

col1   Mcol2 col3  
------ ----- ----- 
A      2     trout
B      1     bass
C      1     carp
C      2     tuna
D      1     salmon

As you can see, I still get C, 1, carp, when I’m only wanting C, 2, tuna.

I’ve considered trying to do something like

select col1, col2, col3
from mytable
where 
    col1-n-col2 in (
        select col1, max (col2) as mCol2
        from mytable)
group by col1, col2

But I don’t think that’s legal in SQL. What obvious solution have I missed?

Answer 1

you were close

select t.col1, t.col2, t.col3
from mytable t,
    (select col1, 
        max (col2) as mx 
    from mytable
    group by col1) m
where m.col1 = t.col1
and m.mx = t.col2