Can anyone help me a bit.

i am using this basic script for my goal:

<http://www.aspsnippets.com/Articles/Check-UserName-Availability-in-ASP.Net-using-JQuery.aspx>

now what i want to achieve is , it should check in 3 tables for same username and confirm shows:

In which table it exist and in which it don't.

So how to achieve that goal can anyone just tell me i am thinking to :

Make a table (4th) with a primary key as username and it will contain usernames.

Now in other 3 tables i will make those tables username as foreign key and link the 4th table username with it.

Now my question is : What stored procedure function to call to achieve that goal ?