Mysql Timestamp comparison to delete when mysql timestamp > 20 minutes
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I want doing something not complicated but i do not succed even i tried a lot of things....

First of all, i have a database mysql with a row in timestamp type. I insert into it elements with a date like this:

    $date = date('Y-m-d H:i:s', time());
    $req =mysql_query("INSERT INTO my_table (id, departement, voie, date,message) VALUES ('', '$departement_token', '$voie_token','$date' , '$message_token')");

The result of this code line is a date element like this : 2012-07-19 20:18:17

I want to delete all elements with a date > current date + 20 minutes and i do not succed...

I tried this:

    mysql_query("DELETE FROM my_table DATE_SUB(date,INTERVAL 20 MINUTE)  ORDER BY date");

And this:

    $req =mysql_query("DELETE FROM my_table date >= TIMESTAMPADD(MINUTE,-20,NOW()) ORDER BY date");

And this:

    $timePlus20min = time() + 1200;
    //et on compare les deux dates
    $req =mysql_query("DELETE FROM my_table UNIX_TIMESTAMP(date) >= '$timePlus20min' ORDER BY date");

And nothing work !!!!!
Could you help me please, i think is not difficult but i m out...
(sorry for my english im french)