解决方法
BEGIN TRANSACTION
UPDATE t1
SET Description = t2.Description
FROM db1.dbo.foo t1
JOIN db2.dbo.foo t2
ON t1.ItemID = t2.ItemID
SELECT * FROM db1.dbo.foo
--prevents changes from being committed
ROLLBACK
BEGIN TRANSACTION
UPDATE t1
SET Description = t2.Description
FROM db1.dbo.foo t1
JOIN db2.dbo.foo t2
ON t1.ItemID = t2.ItemID
SELECT * FROM db1.dbo.foo
--prevents changes from being committed
ROLLBACK
