Checking an input param if not Null and using it in where in SQL Server

Question

What is the best way to include an input param in the WHERE clause but exclude it if it is null?

There are a number of ways I believe, but I can\'t seem

Answer 1

You can use IsNull

 where some_column = IsNull(@yourvariable, 'valueifnull')

EDIT:

What you described in the comment can be done like:

where (@code is null or code = @code)

Answer 2

Here's another approach

SELECT * FROM Thingies WHERE ( @thingId IS NULL OR ThingID = @thingId )