Mysql select with exceptions

I want to create a table with data from mysql, but with some exceptions. More exactly, I have:

$data = mysql_query("SELECT `id` FROM `dates` WHERE `user`='x'");
$exceptions = mysql_query("SELECT `id` FROM `exceptions` WHERE `user`='x'");

I want to make something like:

for($j=1; $date = mysql_fetch_object($data); $j++)

But I don't want to get rows from data, with the same ids from $exceptions, something like:

if($data->id == $exceptions->id) return null;

开发者_JAVA百科So if in $data I have 1, 2, 3, 4, 5 and on $exceptions I have 4, i want to return just rows 1, 2, 3, 5

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You only need one query:

SELECT id FROM dates WHERE user = 'x' AND id NOT IN (SELECT id FROM exceptions WHERE user = 'x'))

There are multiple ways to write that query, too. You should always aim to retrieve only the data you need.