Date: 2016oct10 Product: mysql Keywords: create, replace, upsert Q. How can I do: If (key exists) update else insert A. Mysql: Use INSERT ... ON DUPLICATE KEY UPDATE http://dev.mysql.com/doc/refman/5.7/en/insert-on-duplicate.html This is atomic and doesn't require a transaction from the programmer. Unfortunately the syntax requires that you code insert syntax and an update. Postgresql: Use INSERT ... ON CONFLICT UPDATE https://www.postgresql.org/docs/current/static/sql-insert.html#SQL-ON-CONFLICT