On Fri, 9 Jul 2004 14:01:46 +0100, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > Nearly always, but not absolutely always. I have a table with columns > primary start > primary finish > secondary start > secondary finish > > Since it is defined that the distance between start and finish is the same > for both primary and secondary, this is denormalised, since secondary > finish is always given by secondary start + (primary finish - primary > start). However, I want to use all four fields as indexes, including > secondary finish. Does any database allow indexes on complex functions of > columns rather than on columns themselves?
Sure. In PostgreSQL I would do: CREATE INDEX the_idx ON table (secondary start + primary finish - primary start); > Or is this just a defect in MySQL? The absence of an optimization is the absence of an optimization, not a defect. Jochem -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
