How to use SQL - INSERT...ON DUPLICATE KEY UPDATE?

Question

I have a script which captures tweets and puts them into a database. I will be running the script on a cronjob and then displaying the tweets on my site from the database to prevent hitting the limit on the twitter API.

So I don't want to have duplicate tweets in my database, I understand I can use 'INSERT...ON DUPLICATE KEY UPDATE' to achieve this, but I don't quite understand how to use it.

My database structure is as follows.

Table - Hash id (auto_increment) tweet user user_url

And currently my SQL to insert is as follows:

$tweet = $clean_content[0];
$user_url = $clean_uri[0];
$user = $clean_name[0];

$query='INSERT INTO hash (tweet, user, user_url) VALUES ("'.$tweet.'", "'.$user.'", "'.$user_url.'")';
mysql_query($query);

How would I correctly use 'INSERT...ON DUPLICATE KEY UPDATE' to insert only if it doesn't exist, and update if it does?

Thanks

Answer 1

you need some UNIQUE KEY on your table, if user_url is tweer_url, then this should fit (every tweet has a unique url, id would be better).

CREATE TABLE `hash` (
  `user_url` ...,
  ...,
  UNIQUE KEY `user_url` (`user_url`)
);

and its better to use INSERT IGNORE on your case

$query='INSERT IGNORE INTO hash (tweet, user, user_url) VALUES ("'.$tweet.'", "'.$user.'", "'.$user_url.'")';

ON DUPLICATE KEY is useful when you need update existing row but you want to insert just once