An “upsert” in the combination of an INSERT and UPDATE statement, built into a single clause. The usert model is especially useful in data warehouses where you need the following logic: IF FOUND THEN UPDATE ELSE INSERT; Upserts are great for processes that you normally require multiple insert as select statements IAS) statements. This is because upserts remove the need for row-at-a-time processing and enable the entire transaction as a single set.
