I can't think of a way to do it with a constraints,
but it should be easy enough to do with a trigger,
raising your own error with your own message.
What you are describing is a de-normalised table, where the value of a
column can be defined/predicted based on the value in another column.
Instead of creating a constraint, could you either take out the version
column (in it's own table with a start date and end date for example)
or take out the symbol column (in another table with other columns that
are wholy dependent on train id.
Received on Mon Oct 24 2005 - 12:09:02 CDT
