If is not uncommon to have a field that, if it has a value, must have a valid one. A common one would be a State/Province field that must be a valid State/Province, but can be null when you have no address filled in.
To do this Check the data, if any, in the FK side for invalids, and correct them Create a Foreign Key on the column, but do not define the column as not null. This is much more efficient than a rule. Charles Parks <[EMAIL PROTECTED]> wrote: >If the user will have a chance of not knowing the correct answer except that >it must exist in a certain list would it be better to have no referencing? > >Charlie >-----Original Message----- >From: Walker, Buddy [mailto:[EMAIL PROTECTED]] >Sent: Monday, February 03, 2003 7:55 AM >To: [EMAIL PROTECTED] >Subject: [RBASE-L] - RE: Verify value or is null > > >Charlie > �What I use is Primary and Foreign Keys. I wouldn't suggest storing a null >value as a primary key but use something that you know won't be input. For >instance if the primary key is idnumber and it is integer then maybe make >use -1 > >Buddy > > >-----Original Message----- >From: Charles Parks [mailto:[EMAIL PROTECTED]] >Sent: Monday, February 03, 2003 8:48 AM >To: [EMAIL PROTECTED] >Subject: [RBASE-L] - Verify value or is null > > >Is there a way to create a rule with a where clause that will allow entry to >made into the table if the value exists in another table or if the value is >null? > >I thought it would be something like this: >WHERE EXISTS (SELECT Column1 FROM Table1 WHERE Table1.Column1 = >Table2.Column2 ) or Table2.Column2 is null >but that where clause is not working. > >Is possible to just store a null value in the lookup table or should I just >set a default value in the primary table? > >Thanks, >Charlie > > -- Albert Berry Full Time Consultant to PSD Solutions 350 West Hubbard, Suite 210 Chicago, IL 60610 312-828-9253 Ext. 32 __________________________________________________________________ The NEW Netscape 7.0 browser is now available. Upgrade now! http://channels.netscape.com/ns/browsers/download.jsp Get your own FREE, personal Netscape Mail account today at http://webmail.netscape.com/
