Using group by on two fields and count in SQL

Question

I have a table in my mysql db that has two columns: group and subgroup. See below.

 group, subGroup
 grp-A, sub-A
 grp-A, sub-A
 grp-A, sub-B      
 grp-B         


        

Answer 1

You must group both columns, group and sub-group, then use the aggregate function COUNT().

SELECT
  group, subgroup, COUNT(*)
FROM
  groups
GROUP BY
  group, subgroup