Question

I have table in an MS Access database that looks like this:

ID    Symbol    Direction    Start_val    End_val    AW    
1     ABC       up           100          120        10    
2     ABC       up           110          130        11    
3     XYZ       down         350          380        15    
4     XYZ       down         340          390        15    

I am trying to delete duplicate symbols and directions that have overlapping start_val and end_val and the highest AW. For example in the table above the data matching id 1 has a start_val and end_val that overlap the start_val and end_val of id 2. Since id 1 has a smaller AW i want to delete that. For id 3 and 4, the start_val and end_val overlap but the AW is the same, so the smallest id is deleted.

Answer 1

This should do the trick:

delete tablename
from tablename t1
inner join tablename t2 on t1.Symbol = t2.Symbol
                           and t1.Direction = t2.Direction
                           and t1.Start_val >= t2.Start_val
                           and t1.End_val <= t2.End_Val
                           and t1.AW <= t2.AW

Making the inner join with the same table with the restrictions:

• equal Symbol;
• equal Direction;
• Bigger (or equal) Start_val;
• Lesser (or equal) End_val;
• Lesser (or equal) AW.

will get you the list of rows that you want to delete.