Performing an UPDATE or INSERT depending whether a row exists or not in MySQL

Question

In MySQL, I'm trying to find an efficient way to perform an UPDATE if a row already exists in a table, or an INSERT if the row doesn't exist.

I've found two possible ways so far:

1. The obvious one: open a transaction, SELECT to find if the row exists, INSERT if it doesn't exist or UPDATE if it exists, commit transaction
2. first INSERT IGNORE into the table (so no error is raised if the row already exists), then UPDATE

The second method avoids the transaction.

Which one do you think is more efficient, and are there better ways (for example using a trigger)?

Answer 1

INSERT ... ON DUPLICATE KEY UPDATE