Here is an example:

WHEN

SOURCE NOT MATCHED THEN

    --DELETE

    UPDATE SET

    d

.Deleted = 1

The above code updates the status of the column "deleted" to 1, instead of physically deleting the record.

If you are doing this,  you need another change at the JOIN condition, to skip the deleted records.

USING

OrderInfo AS o

ON

(d.OrderNumber = o.OrderNumber AND d.ItemNumber = o.ItemNumber AND d.Deleted = 0)