Question

Whats the purpose of having single column table (identity column)? Is there a good use-case available?

Is it really a good practice?

Answer 1

I think people use this to replicate Oracle’s SEQUENCE. Basically they want a single unique identifier for any entity they create in their system, so they have something like this:

CREATE PROCEDURE dbo.GenerateIdentifier
    @Identifier INT OUTPUT
AS
BEGIN
    SET NOCOUNT ON;

    INSERT dbo.SingleColumnTable DEFAULT VALUES;

    SET @Identifier = SCOPE_IDENTITY();
END
GO

Now whenever they want to add a new contact, or customer, or order, etc. they first call this procedure and get the new identifier. Then only one entity in the system will have an identifier = 1, or 2, etc.