Postgres UPSERT (INSERT or UPDATE) only if value is different

Question

I\'m updating a Postgres 8.4 database (from C# code) and the basic task is simple enough: either UPDATE an existing row or INSERT a new one if one doesn\'t exist yet. Normally I

Answer 1

Start a transaction. Use a select to see if the data you'd be inserting already exists, if it does, do nothing, otherwise update, if it does not exist, then insert. Finally close the transaction.