The best way to select rows from several tables? - php

Question

I am creating a php app and am now creating the DB interface code. In my APP their are three tables, user, network, user_network. They have the following columsn:
user<-------------------->user_network<-------------------->network
user_ID un_ID network_ID
user_Name un_Member network_Name
un_Network network_Description
I have created the following query which querys the user_network table and returns the ID's of all networks which the user is a member of:
$STH = $DBH->query("SELECT * FROM user_network WHERE nm_Member ='$userID'");
I then pull the network_ID's from this array using the following code:
$DB_NetworkID = array();
foreach($STH as $row)
{
$DB_NetworkID[$counter] = $row['nm_networkID'];
$counter++;
}
print_r($DB_NetworkID);
The array now holds of all the network IDs that the user is a member of, like so
Array ( [0] => 1 [1] => 3 [2] => 5 [3] => 7 ) //network IDs = 1, 3, 5, 7
I would now like to pull rows from the networks tables, how do i go about about SELECTing rows from the networks database WHERE the ID is contained in the array?
Thanks for any help.

Answer 1

You should use a JOIN instead and make it a single query:
SELECT
*
FROM
user
INNER JOIN
user_network
ON
user.user_ID = user_network.un_ID
INNER JOIN
network
ON
user_network.un_Network = network.network_ID
WHERE
user_ID = '$userID'
That query will give you all networks that a user is member of.

Answer 2

If your problem is the comparison against an array, then an easy workaround is using FIND_IN_SET() like this:
$list = implode(",", $DB_NetworkID); // turns it into "1,3,5,7"
... "SELECT * FROM foo WHERE FIND_IN_SET(network_ID, '$list')";
For better performance you should construct an .. IN (?,?,..) clause however.

Answer 3

Of course using JOIN as "halfdan" said, is the best way.
But I gonna answer your question:
If your array is like this:
$un = Array ( [0] => 1 [1] => 3 [2] => 5 [3] => 7 ) //network IDs = 1, 3, 5, 7
You can use a Foreach like this:
Foreach($un as $key => $value) {
and your query will be like this:
SELECT * FROM network WHERE network_ID ='$value'