SQL aggregation query, grouping by entries in junction table
- by cm007
I have TableA in a many-to-many relationship with TableC via TableB. That is,
TableA TableB TableC
id | val fkeyA | fkeyC id | data
I wish the do select sum(val) on TableA, grouping by the relationship(s) to TableC. Every entry in TableA has at least one relationship with TableC. For example,
TableA
1 | 25
2 | 30
3 | 50
TableB
1 | 1
1 | 2
2 | 1
2 | 2
2 | 3
3 | 1
3 | 2
should output
75
30
since rows 1 and 3 in Table have the same relationships to TableC, but row 2 in TableA has a different relationship to TableC.
How can I write a SQL query for this?
