The upcoming (9.5) version of PostgreSQL will include the long-awaited “UPSERT” functionality, which makes it possible to insert-or-update with a single query.  How is this different from other functionality, such as MERGE? What are the use cases for this functionality? And what should we keep in mind when we use it? In this talk, Peter Geoghegan introduces UPSERT, compares it with other alternatives (including in MySQL), and demonstrates when and why we can look forward to seeing it in the upcoming version of PostgreSQL.