SQL select all if parameter is null else return specific item

Question

Is there a way to write the following script so that it returns all products if the ProductID variable is null ? And return a specific product when the product it is not nul

Answer 1

Try this

DECLARE @productID INT = NULL

SELECT 
    ProductID,
    ProductName,
    ProductDesc 
FROM
    product 
WHERE 
    ProductID = isnull(@productID,ProductID)