Question

I have a SQL insert statement that looks something like this?

$SQL = "INSERT INTO profile_answers (user_id, profile_id, question_id, question_answer, timestamp) VALUES ($user_id, $profile_id, {$i}, $answer, NOW())";

This is called three times, each time altering the question ID but the user_id and profile_id are the same. Is it possible to prevent duplicate entries using ‘ON DUPLICATE KEY UPDATE by first looking at the first two fields (user_id, profile_id)?

A entry in my DB would look like this:

user_id profile_id  question_id
5           7                 1
5           7                 2
5           7                 3

Is it possible to prevent a second insert of ( 5, 7, 1) for example?

Answer 1

alter table profile_answers add unique index(user_id, profile_id, question_id);

This will prevent inserting the same values twice for these columns.