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

You can create a PRIMARY or UNIQUE key out of multiple columns (called a composite key) in MySQL, which'll allow ON DUPLICATE KEY to work just fine.

// create a composite index
CREATE INDEX my_composite_index ON my_table (column1, column2);

// insert or update
INSERT INTO my_table (column1, column2) VALUES ('value1', 'value2') ON DUPLICATE KEY UPDATE column3=column3+1;

Answer 2

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

Answer 3

Edit: Ignore my suggestions

You can use a composite key as ceejayoz said, however I think you need REPLACE INTO instead of UPDATE ON DUPLICATE KEY because REPLACE also inserts if no duplicate is found.

Note: I don't know the workings of UPDATE ON DUPLICATE KEY but it sounds like it doesn't perform inserts.