Upsert on a range - sql-server-2008

Question

I'm aware of this:
IF EXISTS (SELECT * FROM table WHERE pk = #pk)
BEGIN
--Update
END
ELSE
BEGIN
--INSERT
END
But this works for one row. Let's say I have a table min_max M and a temp table __MinMaxImport T. I want to INSERT from T to M, but UPDATE when the pair branch_no/product already exists in M.
INSERT:
INSERT INTO min_max
(user_no, branch_no, product, min_stock, max_stock)
SELECT
#user_no, _branch_no, _product, _min_stock, _max_stock
FROM
traxs_temp..__MinMaxImport
WHERE
session_id = #session_id
UPDATE:
UPDATE min_max SET
date_time = GETDATE(),
user_no = #user_no,
min_stock = _min_stock,
max_stock = _max_stock
FROM
min_max M
INNER JOIN traxs_temp..__MinMaxImport T ON T._product = M.product
AND T._branch_no = M.branch_no
WHERE
session_id = #session_id
What is the best solution to do this? I read about MERGE but I'm not sure how to use it.

Answer 1

MERGE should be able to do it.
MERGE INTO min_max
USING
(
SELECT
#user_no AS _user_no, _branch_no, _product, _min_stock, _max_stock
FROM
traxs_temp..__MinMaxImport
WHERE
session_id = #session_id
) AS Src
ON
(min_max.branch_no = Src._branch_no) AND
(min_max.product = Src._product)
WHEN MATCHED THEN
UPDATE SET
date_time = GETDATE(),
user_no = Src._user_no,
min_stock = Src._min_stock,
max_stock = Src._max_stock
WHEN NOT MATCHED BY TARGET THEN
INSERT
(user_no, branch_no, product, min_stock, max_stock)
VALUES
(Src._user_no,
Src._branch_no,
Src._product,
Src._min_stock,
Src._max_stock)
;