constraint

Can someone please tell me some more about the use of "constraints". I read all about it in the manuals, but what I'd like to know is what's the advantage of using constraints over unique indexes, besides of them being a part of the "create table" statement ? Does the database engine handle them in a better way than self-created indexes, because I understand that the engine implements them just as indexes ? Are there any differences between the Standard Engine and On-Line in handling constraints ? Thanks to help me out on this. -- Marien de Clercq ___ Intergraph European Mfg. bv. /|/| // "Don't believe the hype Nijmegen - The Netherlands / | __// is a sequel" m_clercq@nijmeg.nijmeg.ingr.com / |/_/ \\___ Snap