MySQL 'UPDATE ON DUPLICATE KEY' without a unique column?

Question

What are peoples\' thoughts on the most performance efficient way to do the following query:

• 3 column table

• if the combination of col_

Answer 1

Most efficient way is to create UNIQUE KEY and use ON DUPLICATE KEY UPDATE.

Slower way is to:
LOCK TABLE
SELECT TABLE (you need an index anyway for the best performance)
if exists, UPDATE
else INSERT
UNLOCK TABLES