Question

Could I get some help creating this query please?

Users book product video slots to advertise ONE product video. The booking table captures these bookings. Booking spots are allocated to a user not to a product or video.
The #1-ranked video for the user’s #1-ranked product will be the one that is advertised.

Bookings table

id   user_id   position  
---- -----     --------       
1     100        1             
2     150        2               

Users table
Users can have 1-n bookings

id     name
----   ----
100    John Smith
150    Herby Brown

Products table
A user can have 1-n products

id    name      user_id   rank   
---   ----      -------   ----     
1     bike        100        1            
2     stereo      100        2 
3     computer    100        3
4     notebook    150        1
5     scooter     150        2

Videos table
A product can have 1-n videos

id    name            product_id      user_id   rank   
---   ----            -----------     -------   ----   
1     bike video1        1               100      1            
2     bike video2        1               100      2 
3     computer video     3               100      3
4     notebook video     4               150      1
5     scooter video      5               150      2

So, the query reads, in words:
For each booking record, get the #1 ranked video for the #1-ranked product for the booked user. Order the results by booking position.

Answer 1

SELECT v.id, 
       v.name, 
       v.rank, 
       v.user_id, 
       u.name AS uname 
FROM   videos v 
       JOIN users u 
         ON u.id = v.user_id 
       JOIN bookings b 
         ON u.id = b.user_id 
WHERE  v.product_id = (SELECT id 
                       FROM   products 
                       WHERE  user_id = b.user_id 
                       ORDER  BY rank ASC 
                       LIMIT  1) 
ORDER  BY b.position ASC, v.rank ASC

some simplified query:

SELECT v.id, 
       v.name, 
       v.user_id, 
       u.name AS uname, 
       p.name AS pname 
FROM   videos v 
       JOIN users u 
         ON u.id = v.user_id 
       JOIN bookings b 
         ON u.id = b.user_id 
       JOIN products p 
         ON p.id = v.product_id 
WHERE  v.product_id = (SELECT id 
                       FROM   products 
                       WHERE  user_id = b.user_id 
                              AND rank = 1) 
       AND v.rank = 1 
ORDER  BY b.position ASC