On Fri, 10 Oct 2008 00:35:15 -0700, Darren New <dne### [at] sanrrcom> wrote:

>Likely correct. This doesn't really help too much if you don't have 
>check-constraints tho. 

You would still want a check constraint, driven by the account type.

>Having them in separate tables has the benefit 
>that you don't need to store the empties for fields that aren't 
>applicable, 

Does MySql use much space for null values?  Either way, that's really a non-issue,
compared to the benefit of data integrity.

>and you can add a new type of account without having to frob 
>the big table. 

It boils down to "alter big-table" vs. "create new-table".  With "create new-table",
you'd additionally have to set up foreign key constraints back to the big table's
primary key.  You'd have to
modify the check constraint in either case.

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