I have a table that contains a significant amount of data. The columns are as follows;
ID, WeekNo, Ref, Cost
What I want a query to do is only show me differences in Cost value where the Ref is the same
For example
ID, WeekNo, Ref, Cost
1, 1, ABC, 123
2, 1, DEF, 456
3, 2, ABC, 123
4, 2, DEF...