MySQL: Insert if this ip dont have any records - php

Question

I use:
INSERT INTO `rating` (`name`, `user`, `rating`, `section`, `ip`)
VALUES ('$name', '{$_SESSION['user']}', '$rate', '$section',
'{$_SERVER['REMOTE_ADDR']}');";
I would like to add an if condition in the IF statement so that.
IF SELECT ip from rating
where ip={$_SERVER['REMOTE_ADDR']} AND section=$section AND name=$name
then update ELSE INSERT new row
is it doable or I better code it in php ?
thank you very much
P.s: I know how to do it with php, I want to learn it with MySQL.
Also i require that all 3 name,section,ip matchs not only ip

Answer 1

Assuming you have a unique constraint (UNIQUE index or PRIMARY KEY) on ip, section and name, you can use this syntax:
INSERT INTO `rating` (`name`, `user`, `rating`, `section`, `ip`)
VALUES ('$name', '{$_SESSION['user']}', '$rate', '$section', '{$_SERVER['REMOTE_ADDR']}')
ON DUPLICATE KEY UPDATE user = VALUES(user), rating = VALUES(rating);

Answer 2

To expand on Eric's excellent answer.
To add a unique constraint on each of the columns ip, name, section run the following code on the database
ALTER TABLE `test`.`rating`
ADD UNIQUE INDEX `name`(`name`),
ADD UNIQUE INDEX `section`(`section`),
ADD UNIQUE INDEX `ip`(`ip`);
To run a unique constraint on the combination of columns ip+name+section do:
ALTER TABLE `test`.`rating`
ADD UNIQUE INDEX `name_section_ip`(`name`, `section`, `ip`);
The last thing is probably what you want.
One last thing
I'm not 100% sure, but this usage of {$_SERVER['REMOTE_ADDR']} in the query does not look SQL-injection safe.
Consider changing it into:
$remote_adr = mysql_real_escape_string($_SERVER['REMOTE_ADDR']);
$session = mysql_real_escape_string($_SESSION['user']);
$query = "INSERT INTO `rating` (`name`, `user`, `rating`, `section`, `ip`)
VALUES ('$name', '$session', '$rate', '$section','$remote_adr')";
Finally putting a ";" in a mysql_query() like so mysql_query("select * from x;"); does not work mysql_query() will only ever execute one query and will reject your ;.