Join two tables but exclude rows that match condition in a third table

Question

I want to be able to search users by name and get results back for only for:

1. Those who I am friends with
2. Those who are NOT already aligned with my 'event'.

I have a query that does part #1 successfully:

SELECT u.id, first_name, last_name
FROM user u
JOIN friend f
ON (
    ( f.requester_id = u.id AND f.recipient_id = :my_user_id )
    OR ( f.recipient_id = u.id AND f.requester_id = :my_user_id ) 
    AND confirmed = 1
)
AND (
    ( first_name LIKE :search_input OR last_name LIKE :search_input )
    OR ( CONCAT ( first_name, ' ', last_name ) LIKE :search_input )
)
AND NOT u.id = :my_user_id
ORDER BY last_name
LIMIT 5

Struggling to figure out how to add part #2. Tables look like this:

USER
id | first_name | last_name
-- | ---------- | ---------
0  | John       | Doe
1  | Jane       | Doe
2  | Bob        | Smith
3  | Mike       | Jones

FRIEND
id | requester_id | recipient_id | confirmed
-- | ------------ | ------------ | ---------
0  | 0            | 1            | 1
1  | 3            | 1            | 1
2  | 2            | 3            | 1
3  | 1            | 2            | 1

USER_EVENT
id | user_id | event_id 
-- | ------- | --------
0  | 0       | 43                
1  | 0       | 846                 
2  | 0       | 1058              
3  | 1       | 846    
4  | 1       | 912                 
5  | 2       | 537                 
6  | 3       | 846 

Sample data a query might get:

:search_input (e.g. '%bob%')
:my_user_id (e.g. 3)
:event_id (e.g. 846) 

Answer 1

you can simply add another clause to your query: AND user_id NOT IN (SELECT user_id from USER_EVENT where event_id = :event_id)

Full query:

SELECT u.id, first_name, last_name
FROM user u
JOIN friend f
ON (
    ( f.requester_id = u.id AND f.recipient_id = :my_user_id )
    OR ( f.recipient_id = u.id AND f.requester_id = :my_user_id ) 
    AND confirmed = 1
)
AND (
    ( first_name LIKE :search_input OR last_name LIKE :search_input )
    OR ( CONCAT ( first_name, ' ', last_name ) LIKE :search_input )
)
AND NOT u.id = :my_user_id
AND user_id NOT IN (SELECT user_id from USER_EVENT where event_id = :event_id)
ORDER BY last_name
LIMIT 5