[SOLVED] Cross-table Selection

[sciencebear]

I'm trying to run a query. Basically, the first table is a friends system. It has a column for a user and a column his/her friend. What I want to do is select all of the friends from the second column for whenever the first column is who is logged in. I can do, this, and have no problem with it. However, with these names, I want to use them as the parameters in a different table and select every row where the information in one column matches any of the friends selected from the first table. I have an idea of how this would work, but I am not sure. Does anyone know for sure how to do this?

[Ken2k7]

I don't know if this works, but logic wise, it seems right.

 

SELECT t2.*
FROM `table_two` t2
WHERE t2.column_name IN (
     SELECT t1.friend
     FROM `table_one` t1
     WHERE t1.user = '$user'
);

 

[sciencebear]

Nah, it didn't work.

 

Basically, what I really need to know is this:

 

I select an array of all the different friend ids from the first table. I need to use this to select all the rows in the second table where the data from a column matches any of the ids in the array, but I don't know how to do this.

[Ken2k7]

Can you show me what you have right now? By the way, in my query, there is a variable $user. Take the line out if it doesn't apply.

[sciencebear]

Alright here goes.

 

Table 1-friends

col1:userid

col2:friendid

 

Table 2-post

col1:id

col2:userid

col3...

col4...

(The other two columns aren't used for selection, but they need to be selected.)

 

This is basically what I have so far:

 

($userid is supplied when logged in)

 

$row1 = mysql_query("SELECT friendid FROM friends WHERE userid = '$userid'");

$row2 = mysql_fetch_array($row1);

$row3 = mysql_query("SELECT MAX(id) FROM post WHERE userid = '$row2'");

$row4 = mysql_fetch_array($row3);

[Ken2k7]

Did you try my SQL? Can you show me the code using the SQL I wrote?