CONSTRAINT question

This is a question that _should_ easily be answered in the documentation, but it was apparently written by drunken baboons. In several places we have noticed "CONSTRAINT" as an optional keyword to specify contraints on one or more columns. It is followed by a group of identifiers. HOW DO YOU _DEFINE_ A CONSTRANT? We've checked every book in our release and while we know how to define a table with constrants, add constrants to an existing table, remove constrants from a table, construct valid names for constrants, etc., _NOWHERE_ does it say how to define one. BTW, I even checked much of the documentation for indices, since they are probably related. (I'm posting this instead of simply contacting Informix since I suspect I'll get email warning us about other missing documentation). -- Bear Giles bear@fsl.noaa.gov -<My views rarely reflect those of my employer or the Federal government>-