Interesting, PostgreSQL works just like you said. However MySQL doesn't. I've just tried it, and MySQL blocks the UPDATE until the first transaction (DELETE, I

Interesting, PostgreSQL works just like you said. However MySQL doesn't. I've just tried it, and MySQL blocks the UPDATE until the first transaction (DELETE, INSERT) is finished (like PostgreSQL), but after the commit, the UPDATE statement updates the newly inserted row. It seems MySQL firstly searches the table for the row and then attempts to acquire a lock on it (thus waits for the DELETE, INSERT to finish, as it's locked the row being DELETEd), and, after the lock has been acquired, searches the table again for rows matching the query in order to perform it.