Question

I have this trigger which works functionally (as far as I can tell by my tests) but I strongly suspect I can simplify the code by using IF UPDATE… I just don’t fully understand how it works. I seem to do best undestanding triggers in terms of the inserted and deleted tables.

Can this trigger be simplified in the way I just mentioned (or any other way that improves the readability)?

CREATE TRIGGER [dbo].[tr_Affiliate_IU] 
   ON  [dbo].[Affiliate] 
   AFTER INSERT, UPDATE
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    -- Get the current date.
    DECLARE @getDate DATETIME = GETDATE()

    -- Set the initial values of date_created and date_modified.
    UPDATE
        dbo.Affiliate
    SET 
         date_created = @getDate
    FROM
        dbo.Affiliate A 
        INNER JOIN INSERTED I ON A.id = I.id
        LEFT OUTER JOIN DELETED D ON I.id = D.id
    WHERE
        D.id IS NULL

    -- Ensure the value of date_created does never changes.
    -- Update the value of date_modified to the current date.
    UPDATE
        dbo.Affiliate
    SET
         date_created = D.date_created
        ,date_modified = @getDate
    FROM 
        dbo.Affiliate A 
        INNER JOIN INSERTED I ON A.id = I.id
        INNER JOIN DELETED D ON I.id = D.id 
END

Answer 1

If updated(column_name) cannot help as it merely states that column participated in a query that raised the trigger. The update part of the trigger can be shortened by use of case statement to help decide which date date_created is going to hold.

CREATE TRIGGER [dbo].[tr_Affiliate_IU] 
   ON  [dbo].[Affiliate] 
   AFTER INSERT, UPDATE
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    -- Get the current date.
    DECLARE @getDate DATETIME = GETDATE()

    -- Set the initial values of date_created and date_modified.
    UPDATE
        dbo.Affiliate
    SET 
      -- If there is a record for this ID in Deleted
         date_created = case when D.id is not null 
                          -- Take date of creation from Deleted
                             then D.date_created 
                             else @getDate 
                             end
        ,date_modified = @getDate
    FROM
        dbo.Affiliate A 
        INNER JOIN INSERTED I ON A.id = I.id
        LEFT OUTER JOIN DELETED D ON I.id = D.id
END