Thanks you all….

This opens up a wide range of options for solving complex problems with good performance.

Please let us know when you find exciting ways to use this feature.
Phil

I’d try the same and it should work — at least at i 6.1 and later, which might not be feasible for this question.

Visual Explain should tell all quickly.

Tom

But, if that’s impossible, I would use a view of the physical including this “Field” definition or a select in RPG including the “Field” definition using the physical file or the view.
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In either case the “Field” is used in the select , where, and order by clauses. with the index matching the order by rules with this “Field” first .. then I would hope the optimizer would choose the indexed path.

Phil

I can imagine an index, but I’m not clear how to use it. The CURSOR SELECT would access either the base table or the view.

The ORDER BY could specify the derived column of the view, but that might not be seen as matching the index. I’d like to think that the optimizer is smart enough.

Or it could specify an expression that matched the index. That might mean that the base table would need to be in the SELECT, but then the view wouldn’t be useful. Or I suppose that the view could present both the base column and the derived column value — except then the view wouldn’t be needed at all because the SELECT could have the same items in its column list.

Maybe not a bad thought at all. It’d be worth it just to see how it needed to be done.

I’d probably still put more effort into correcting the troublesome database design so that none of this would even be needed. But it’s interesting looking at how to make it work.

Tom

In V6R1, it’s documented as possible. You can specify an expression in place of a column name. The list of excluded builtin functions does not include DEC() nor TRIM(), so I’d expect it to work.

Before 6.1, you must reference a column name from the base table (according to the SQL Reference).

Tom

The first value has seven characters, and the second one has only six characters. Unless this is a variable length field, the second value is padded with a blank on the right.

But you can create a SQL VIEW over the columns to interpret the character values as numeric:

dec(trim(charval),10,0) as NumVal 

That converts the ‘charval’ column to a ‘NumVal’ column for presentation. You can specify an ORDER By to read the view. With multiple columns, though, and with a few million records, it’s going to cost a lot of processing time unless this is a one-time run or it’s very infrequent.

Personally, I would probably push forcefully to correct the data. If the user wants it ordered numerically, then the data should be numeric.