WHERE query inside an AND statement? PHP/PDO/MySQL - php

Question

I have 2 tables on my website, a users table and a user_friendships table each structured as so...
Users
id | user_id | credits_bank | credits_offered
User Friendships
id | user_id | user_followed_id
When my user logs in he is presented with a list of other users on the website - the list of other users are those who are stored in the users table and have a greater value in the credits_bank table than that of the credits_offered table.
When a friendship is created, the session users id is stored in the user_friendships table, and the id of the other member he followed is also stored in the user_friendships table under the column user_followed_id.
The problem is I now need a query to return all users who have move credits_bank than credits_offered and users that aren't already in the user_frienships table in the same record as the session user.
I'm currently using...
SELECT DISTINCT u.*
FROM users u
LEFT JOIN user_friendships uf ON u.user_id = uf.user_followed_id
WHERE u.user_id <> ?
AND u.credits_offered <= credits_bank
AND uf.user_followed_id IS NULL
Update
I want to see a list of users whose credits_bank is a greater value than credits_offered and I only want to show them if they dont already exist in a record in my user_friendships table in the same row as my session user.
Users
id | user_id | credits_bank | credits_offered
___________________________________________________
1 123 10 2
2 231 6 3
3 312 6 5
4 213 2 1
User Friendships
id | user_id | user_followed_id
___________________________________________________
1 123 231
2 123 312
Result
If session user_id = 123 then...
user_id 231 and 312 WOULDN'T show as they are in the user friendships table alongside session user id
user_id 213 WOULD show as they have more credits_bank than credits_offered and arent in friendships table
IF the session user_id was 312 then he would see all results as he isnt friends with anybody in the user_friendships table...

Answer 1

As far as I can tell, you're close. If the user id of the current user is called SESS_USER_ID, something like this should work for you;
SELECT DISTINCT u.*
FROM users u
LEFT JOIN user_friendships uf
ON uf.user_followed_id = u.user_id
AND uf.user_id = SESS_USER_ID
WHERE u.credits_offered <= credits_bank
AND uf.user_followed_id IS NULL
AND u.user_id <> SESS_USER_ID
(note that SESS_USER_ID is used twice in the query to make it simple)
An SQLfiddle to test with.

Answer 2

Try this:
SELECT u.id, u.user_id, u.credits_bank, u.credits_offered
FROM users u
WHERE u.credits_bank>u.credits_offered
AND u.user_id = [ENTER LOGGED IN USERS ID HERE]
AND u.user_id NOT IN (
SELECT f.user_ol
FROM user_friendships f
)
Let me know if you have any issues
EDIT
Latest SQL:
SELECT u.id, u.user_id, u.credits_bank, u.credits_offered
FROM users u
INNER JOIN user_friendships f
ON f.user_followed_id = u.user_id
AND u.credits_bank > u.credits_offered
AND f.user_id != [CURRENT_USER_ID]
AND u.user_id != [CURRENT_USER_ID]