Question

I have this little bit of code that I can’t quite work correctly. The part giving me trouble is this:

IF( Class_Subset = @prevSub AND RegNum = @prevNum AND `DRI` >99.99 ,
@Platinum :=@Platinum + 1 ,''  )

What I need to do is tell the @Platinum to reset back to zero once the Class_Subset, or RegNum conditions are no longer met.

Any ideas?

Whole code:

SELECT  
 Harley.Hgt, Harley.RegNum, Harley.Callname, Harley.OLastname,  
 Harley.Tpe, Harley.Points, Harley.Class, Harley.Total_Points,  
 Harley.Title, Harley.Platinum, Harley.Silver_Purple,  
 Harley.Date_Earned, Harley.Judge, Harley.HostClub, Harley.DRI,  
 Harley.Class_Subset, Harley.IncorrectRegNum, Harley.MemNum, Harley.ID
FROM
 (
   SELECT
    Hgt, RegNum, Callname, OLastname, Tpe, Points, Class,  
    Total_Points, Title, Silver_Purple, Date_Earned, Judge,  
    HostClub, DRI, Class_Subset, IncorrectRegNum, MemNum, ID, 
    IF (
     Class_Subset = @prevSub  
     AND RegNum = @prevNum  
     AND `DRI` > 99.99,  
     @Platinum := @Platinum + 1,  
     0
    ) AS Platinum,  
    @prevSub := Class_Subset,  
    @prevNum := RegNum
   FROM  
    Harley,  
    (  
      SELECT @Platinum := 0, @prevSub := '', @prevNum := ''  
    ) r  
   ORDER BY RegNum, Class_Subset, Date_Earned  
 ) Harley

This is what the file looks like, you can see why it needs to remember the variable while the RegNum and Subset match, but then reset to 0 once they change:

sample data http://nadacforum.com/Platinum.png

Answer 1

I think I now see the issue.

The row set where Platinum is being calculated is ordered by RegNum and Class_Subset (in particular), which is fine as the calculation does rely on those columns being sorted. But the IF() condition also involves the DRI column, and, as can be seen on your screenshot, a sequence of DRI values greater than 99.99 may be interrupted within a single group of (RegNum, Class_Subset). When it is reinstated, you need the Platinum values to carry on, not to reset to 1.

Therefore, your @Platinum expression should be a bit more sophisticated. Here’s one way of changing it:

@Platinum := IF (
 Class_Subset = @prevSub  
 AND RegNum = @prevNum  
 AND `DRI` > 99.99,
 @Platinum,  
 0
) + (`DRI` > 99.99) AS Platinum,