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 possi

Answer 1

REPLACE INTO would be a solution, it uses the UNIQUE INDEX for replacing or inserting something.

REPLACE INTO
    yourTable
SET
    column = value;

Please be aware that this works differently from what you might expect, the REPLACE is quite literally. It first checks if there is a UNIQUE INDEX collision which would prevent an INSERT, it removes (DELETE) all rows which collide and then INSERTs the row you've given it.

This, for example, leads to subtle problems like Triggers not firing (because they check for an update, which never occurs) or values reverted to the defaults (because you must specify all values).