So as a re-cap of my strategy for handling Form Fields which may be blank - especial ones that are often blank...
1.) When a field has a finite number of choices (e.g. gender), try assigning a value for no response (e.g. 0=unknown, 1=male, 2=female)
2.) When a field is larger and has a high probability of not being answered, attempt to create a one-to-many or many-to-many relationship so that there is one record for each response, and a record is only created when there is a value - as opposed to a lonely column with a bunch of NULL's. (I did this for my "Question & Answer" section which hold large responses, but which may often be left blank.) ( MEMBER -||-----0<- ANSWER ->0-------||- QUESTION )
3.) If a field or a series of fields (e.g. About-Me section) has a high probability of being blank, consider breaking off said fields into a separate table which forms a one-to-one relationship with the main table (e.g. MEMBER -||-----||- MEMBER_ATTRIBUTES )
4.) Use NULL's freely as long as they truly represent fields and values where the "value is unknown"
How does that sound, r937?