Question

I have a problem with this SQL Grouping.

If i have a table with 3 columns. Key is a unique key for every record. Type is the type of record and Version is the version of the type.

ID    Type      Version
------------------------
1      A          200
2      A          100
3      B          200
4      B          200
5      B          100

I need to get 1 row for each version of each type

so it would look something like

ID    Type       Version
------------------------
1      A           200
2      A           100
3      B           200
5      B           100

I know I need to group by the Type and version but I cant seem to figure out how to get the unique key for each Type and Version since they are on the same table

SELECT Type, Version FROM TableName GROUP BY Type, Version 

Gets me all the unique Types and Versions, but I cant figure out how to finish off the query.

Answer 1

you mean the unique ID?
you need to use an aggregation function like MAX, MIN, SUM, AVG

you cant get an unique value. Think about it, if you have:

1   A   100
2   A   100
3   A   100

you want only one row with

A 100

but whats the logic to define the ID between 1,2 and 3? It isnt unique. That’s why you need a MAX or MIN or any other aggregation function