In an Client-Server application where the customer insists on a specific Primary key (say ID C(10)), I wish to discuss the pros and cons of the following methods of inserting a new record.

(a) Check if the new primary key (Say ID = "JFK"), exists in the Backend table using INDEXSEEK or SELECT-SQL, then lock the WHOLE table while the INSERT is being performed.
(b) Try to insert the record without checking, trap and deal with any error returned ie "Duplicate Primary key"
(c) Any other suggestions?