Alastair - when I have to force an FK I use a 0 "Unknown" and use zero as the equivalent to IS NULL, and define the column as NOT NULL. I have found over the years that this is a more foolproof method than allowing NULL FKs. FWIW
"Alastair Burr" <[EMAIL PROTECTED]> wrote: >Hi all, > >This rule has worked correctly for months until I restored the database from >a backup today: > >MESSAGE : �Duplicate combination: Group Sequence > �TABLE : �Images � �Row is added or changed if condition SUCCEEDS > �WHERE : �NOT (( Images.Group_Number * 1000) + Images.Group_Sequence) IN > � � � � � (select (( Images.Group_Number * 1000) + Images.Group_Sequence) > � � � � � from Images where Group_Number > 0) > >Now it won't let me amend rows where the Group_Number and Group_Sequence are >both zero. > >It is intended to ensure that I cannot have duplicate sequence numbers where >there is a group number above zero. > >Both columns default to zero to avoid nulls so zero means no group. There >are many rows with no group so a constraint is not possible. Group_Sequence >can be from 1 to 999 when there is a Group_Number. > >Can anybody see anything wrong with it or shed some light on why a restore >might have affected it? > >Thanks in advance for any suggestions, >Regards, >Alastair. > > >---------------------------------- >A D B Burr, >St. Albans, UK. >---------------------------------- >[EMAIL PROTECTED] >---------------------------------- > >================================================ >TO SEE MESSAGE POSTING GUIDELINES: >Send a plain text email to [EMAIL PROTECTED] >In the message body, put just two words: INTRO rbase-l >================================================ >TO UNSUBSCRIBE: send a plain text email to [EMAIL PROTECTED] >In the message body, put just two words: UNSUBSCRIBE rbase-l >================================================ >TO SEARCH ARCHIVES: >http://www.mail-archive.com/rbase-l%40sonetmail.com/ > __________________________________________________________________ Your favorite stores, helpful shopping tools and great gift ideas. Experience the convenience of buying online with Shop@Netscape! http://shopnow.netscape.com/ Get your own FREE, personal Netscape Mail account today at http://webmail.netscape.com/ ================================================ TO SEE MESSAGE POSTING GUIDELINES: Send a plain text email to [EMAIL PROTECTED] In the message body, put just two words: INTRO rbase-l ================================================ TO UNSUBSCRIBE: send a plain text email to [EMAIL PROTECTED] In the message body, put just two words: UNSUBSCRIBE rbase-l ================================================ TO SEARCH ARCHIVES: http://www.mail-archive.com/rbase-l%40sonetmail.com/
