Officially introduced in the SQL:2003 standard, and expanded in the SQL:2008 standard, MERGE does an INSERT for new records and an UPDATE of existing records depending on whether or not a condition matches.
Database management systems Oracle Database, DB2, Teradata and MS SQL support the standard syntax. Some also add non-standard SQL extensions that allow for things such as a DELETE action.
MERGE is similar to, but not synonymous with UPSERT.
