Custom PrimaryKey Generation with autoincrement

Question

I need to define and generate primary key for 2 or more tables.

Tables hold same type of data but FOR Some BUSINESS RULES we have to make them separate say like

Answer 1

You can definitely do this with a computed column.

Either, if you stick with your two tables, you could just simply add a single computed, persisted column like this:

ALTER TABLE Local_Customer
  ADD CustomerID AS 'LOC' + CAST(ID AS VARCHAR(7)) PERSISTED

ALTER TABLE International_Customer
  ADD CustomerID AS 'INT' + CAST(ID AS VARCHAR(7)) PERSISTED

If you decide to have a single table with a discrimator column, e.g. "IsDomestic" of type BIT, you could do a single computed column that will use "LOC" or "INT" as prefix, based on the value of the "IsDomestic" column:

ALTER TABLE Customer
  ADD CustomerID AS CASE IsDomestic WHEN 0 THEN 'INT' ELSE 'LOC' END + CAST(ID AS VARCHAR(7)) PERSISTED

Either way - your "ID" field of type INT IDENTITY will be automatically increased for each row, and the computed column will create a more human-readable "CustomerID" automagically, without any further effort on your part.