Bedingte WHERE-Anweisung SQL Server

Probieren Sie es aus, es ist elegant :)

 ALTER PROCEDURE [dbo].[usp_return_countries]
   @CountryID AS INT = 0
 AS
 BEGIN

    SELECT *
    FROM Countries
    WHERE Active = 1
    AND (@CountryID = 0 OR @CountryID = CountryID)

 END