Question

For each ID number, I need to group ID numbers by class values, using the lowest rank when there are duplicate class values…I have tried several joins with no success. Would appreciate a VERY brief description for any code suggested. Thanks!

Table Structure:

ID  Rank    Class
A   1       x
A   2       x
A   3       y
A   4       y
B   1       x
B   2       x
B   3       y
B   4       y

Desired Result:

ID  Rank    Class
A   1       x
A   3       y
B   1       x
B   3       y

Answer 1

You should use an aggregate function MIN() with a GROUP BY the id and class:

select id, min(rank) as MinRank, class
from yourtable
group by id, class

See SQL Fiddle with Demo

| ID | MinRank | CLASS |
--------------------------
|  A |       1 |     x |
|  A |       3 |     y |
|  B |       1 |     x |
|  B |       3 |     y |