I think this is related to my previous question about creating foreign key. If the referenced column is the primary key, does that mean sapdb does a table scan every time it does referential-constraint-check when it creates foreign key?
Thanks, > > PRIMARY KEY columns are not indexed in a normal sense. > The whole primary table is stored according to the primary key sequence. > > If we are talking about referential constraints: > the referenced column(s) given behind REFERENCES have to be the PRIMARY KEY of > the referenced table or they have to be a complete unique index of that table. > > The referencing column(s) (the column(s) from the table for which you write the > current create or alter-statement) need not be the primary key or an unique index. > For performance reasons (for a delete in the referenced table) it is a good idea > to have an index for them (need not be unique), otherwise the delete has to > use table scan during referential-constraint-check (RESTRICT) or -handling > (SET NULL, SET DELETE, CASCADE). > > Elke > SAP Labs Berlin > _______________________________________________ > sapdb.general mailing list > [EMAIL PROTECTED] > http://listserv.sap.com/mailman/listinfo/sapdb.general -- Jenny Zhang Open Source Development Lab Inc 15275 SW Koll Parkway - Suite H Beaverton, OR 97006 (503)626-2455 ext 31 _______________________________________________ sapdb.general mailing list [EMAIL PROTECTED] http://listserv.sap.com/mailman/listinfo/sapdb.general
