I solved another occasional mystery today.
Crystal allows you to put your groups in order based on the summary fields that exist for that group. This feature is in the “Report” menu under the label “Group Sort”. So if you group by customer and subtotal sales for each customer you can put the customers in order based on their sum. You can rank the customers this way in either ascending or descending order.
You are allowed to use any type of summary field for group sorting, and on occasion I have used a summary that is based on a date field. This could be the first (minimum) order date of for each customer or the last (maximum) order date for each customer. I have noticed that sometimes when I rank a group based on one of these date summaries that Ascending seems to behave like Descending or vice versa. For instance I might pick Descending and I expect the groups with the latest dates to be first. Sometimes they are and sometimes they aren’t. Before today I had never taken the time to figure out what was going on. Now I know.
If your summary is the Maximum of a date field, like the last order date for each customer, then setting the group sort to ascending or descending will behave in the expected way. Ascending will put the groups with the earliest summary dates first and descending will put the groups with the later dates first.
But if your summary is the Minimum of a date field, like the first order date for each customer, then group sorting for that field will work in reverse. Ascending will put the groups with later dates first and descending will put the groups with earliest dates first. To get the groups to go the way you want you just have to pick the opposite direction.
A couple of notes:
1) This doesn’t happen with a minimum summary of numbers or strings, just a minimum of dates.
2) You can get the same summary value as the minimum by doing the Nth smallest (with N = 1). If you use the Nth Smallest summary for group sorting it does the ascending/descending the normal way, not reversed like the minimum function.