SQL - Restrict the number of rows returned based on a count of rows

Question

Here is what my data looks like:

item_ID | group_ID | count_of_items_in_group

2|ABC|3

5|ABC|3

9|ABC|3

29|DEF|3

3|DEF|3

4|DEF|3

200|XYZ|2

300|XYZ|2

6         


        

Answer 1

What about using ROW_NUMBER() to enum the number of fields of your data set, partitioned by each group_id.

And after that just return when is just less or equal to 2? or any number that you want

SELECT * FROM 
(
  select item_id, group_id, count_of_items, 
  ROW_NUMBER() OVER(PARTITION BY group_id ORDER BY count_of_items DESC) 
  AS RN
  from items_in_groups
) A
WHERE RN <= 2

Here is the Sql Fiddle