How update Stored Procedure has Optional Parameter?

How can I alter Update Stored Procedure so if developer want to set only Size then he/she does not requireed to pass TimeStamp. Moreover, then what will be execute code for this procedure?

Scenario:

Update TimeStamp = getdate() field whose SizeID = 1 AND Size =Large

Note: This field Parameters and condition parameters must be dynamic and optiona开发者_JS百科ls like in where TimeStamp can also be supplied.

Update Stored Procedure:

ALTER PROCEDURE [dbo].[SP_Sizes_Update]

@SizeID    int,
@Size    varchar(50),
@TimeStamp    datetime

AS

Update Sizes

Set
    Size = @Size,
    TimeStamp = @TimeStamp
Where

SizeID = @SizeID

one way

ALTER PROCEDURE [dbo].[SP_Sizes_Update]
  @SizeID    int,
  @Size    varchar(50) = 'Large',
  @TimeStamp    datetime = null
AS
  Update Sizes
  Set
   Size = @Size,
   TimeStamp = coalesce(@TimeStamp,getdate())
  Where
   SizeID = @SizeID

Just set the parameter to a default value, like this:

ALTER PROCEDURE [dbo].[SP_Sizes_Update]
  @SizeID    int,
  @Size    varchar(50),
  @TimeStamp    datetime = null
AS
  Update Sizes
  Set
   Size = @Size,
   TimeStamp = @TimeStamp
  Where
   SizeID = @SizeID

however, if you want the default value to be a result of a function call, you could use some special value that will be replaced by the function hole, like this:

ALTER PROCEDURE [dbo].[SP_Sizes_Update]
  @SizeID    int,
  @Size    varchar(50),
  @TimeStamp    datetime = null
AS
  if @TimeStamp is null
   set @TimeStamp = getdate()

   Update Sizes
   Set
     Size = @Size,
     TimeStamp = @TimeStamp
   Where SizeID = @SizeID