Using an INSTEAD OF Trigger to Handle a Data Feed

FeedTarget_trigger.sql

-- Listing 10-28: Using an INSTEAD OF Trigger to Handle a Data Feed
CREATE TABLE FeedTarget
(
  ID    int      NOT NULL PRIMARY KEY,
  Descr char (5) NOT NULL
)
GO

CREATE TRIGGER tri_FeedTarget ON FeedTarget INSTEAD OF INSERT
AS

IF @@ROWCOUNT = 0
  RETURN

UPDATE F             -- rows that already exist
SET
  Descr = I.Descr
FROM
    inserted   AS I
  JOIN
    FeedTarget AS F ON F.ID = I.ID

INSERT FeedTarget    -- new rows
SELECT
  ID,
  Descr
FROM
    inserted AS I
WHERE NOT EXISTS
(
  SELECT
    *
  FROM
      FeedTarget AS F
  WHERE
      F.ID = I.ID
)
GO