根据其他查询中的值选择查询

Question

Im not an expert in php, and i looked for something like this, but couldnt find anything (don't know exactly how to search for this, or what the name is).

Case:

I have two seperate tables:

"friends":

id | friend_id | foe_id

"updates":

id | user_id

And this code:

 $selectFriends = "SELECT * FROM friends WHERE friend_id = '".$_COOKIE['id']."' OR foe_id = '".$_COOKIE['id']."'";
$queryFriends = mysql_query($selectFriends)or die(mysql_error());

while($listFriends = mysql_fetch_assoc($queryFriends))
{
    echo "".$listFriends['friend_id']."";
    echo "".$listFriends['foe_id']."";

    $selectUpdates = "SELECT * FROM updates WHERE user_id != ".$_COOKIE['id']." AND user_id IN (' . implode(',', ".$listFriends['friend_id'].") . ') ORDER BY date DESC LIMIT 10";
    $queryUpdates = mysql_query($selectUpdates)or die(mysql_error());
}

I get the right id's that i want in the first query, but now i want to use the id's from the first query in the 2nd query; to select the updates of my "friends". So in short: link the "friend_id" & "foe_id" to the "user_id" from the 2nd table.

Answer 1

Use sub-query, as the question is not that clear I am providing the idea only

SELECT * FROM updates WHERE user_id IN (SELECT friend_id FROM friends WHERE friend_id = '".$_COOKIE['id']."' OR foe_id = '".$_COOKIE['id']."'");

Else you need to do little in PHP. Take all friend_id and foe_id records, prepare a comma separated string in a variable ($var). Use that in the query

SELECT * FROM updates WHERE user_id IN ($var);

you may like to use GROUP_CONCAT as well