Use SQL to identify duplicate records

[rekent]

I have a database that accepts first and last name entries for a primary person and a secondary person.  However, there is a problem that sometimes the secondary person comes back looking to be entered as a separate primary person, which is not permitted.  However, I do not have any data validation or verification to prevent this.  When a new record is created, would I be able to use SQL to check the first and last name combinations entered for the primary and the secondary persons against the names previously entered in the database and create a dismissible dialog popup giving a warning when duplicate names are entered?  Ideally the dialog box would also give a link to go to the record where the duplicate name was previously entered to verify that the individual is the same.

[webko]

Why use SQL for this?

I'd also point out that FirstName / LastName isn't a unique combination anyway - there are several Peter Booth's in my wider family for a start...

If I were to go down this path, then a simple search on FirstName / LastName with a found count of > 0 should suffice