Question

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

• 3 column table

• if the combination of col_1 and col_2 values already exist UPDATE col_3

• else INSERT new row

I assume i need some kind if UPDATE ON DUPLICATE KEY (which i’ve never used before), however I do not have a ‘KEY’ but instead a pair of two values (columns) to make a key…

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;