Question

I am going to be executing an Update stored procedure from .NET. I want the following logic in T-SQL, however I can’t seem to find out how this can be done.

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE PROCEDURE sp_UpdateTable

    @TableID int,
    @StartTime1 datetime,
    @EndTime1 datetime

AS
BEGIN
    SET NOCOUNT ON;

    UPDATE [Table]
       SET [StartTime1] = WAS_PASSED_FROM_CODE(@StartTime1, @StartTime1, [StartTime1])
          ,[EndTime1]   = WAS_PASSED_FROM_CODE(@EndTime1,   @EndTime1,   [EndTime1])
    WHERE TableID = @TableID
END
GO

Okay, so what I am basically looking for is a way to determine whether the parameter was specified from code, (hence WAS_PASSED_FROM_CODE) if the parameter was specified from code, then update that column to the specified value, else, leave intact (update to existing value).

Is this possible?

Note that in this case it is valid for the code to pass NULL, in that case, the column should update to NULL.

Answer 1

Make your parameters default to NULL and then use ISNULL. If the parameter is not specified it will be NULL

Edit: Given that NULL is a valid value, add two additional parameters to marked whether or not the date parameters are specified.

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE PROCEDURE sp_UpdateTable

    @TableID int,
    @StartTime1 datetime,
    @StartTime1Specified BIT,
    @EndTime1 datetime,
    @EndTime1Specified BIT

AS
BEGIN
    SET NOCOUNT ON;

    UPDATE [Table]
       SET [StartTime1] = (CASE WHEN @StartTime1Specified = 1 THEN @StartTime1 ELSE [StartTime1] END)
          ,[EndTime1]   = (CASE WHEN @EndTime1Specified = 1 THEN @EndTime1 ELSE [EndTime1])
    WHERE TableID = @TableID
END
GO