Question

I have a table called friends and a table photos. I’m trying to query friends photos OR the users who has the friends photos. I think I need to alias an inner join on the friends table but not sure

Friends Table
user_id int
friend_id int 
[other attribute field]

Photos Table
id      int
user_id int
[other attribute field]

For example if I want to query friends photos i’d run

SELECT `photos`.`id` FROM `photos` LEFT JOIN `friends` ON (`friends`.`friend_id` = `photos`.`user_id`) WHERE `friends`.`user_id` = 1

Or if I wanted to query just the users table id do

SELECT `photos`.`id` FROM `photos` WHERE `photos`.`user_id` = 1

The problem is when I try to get both in the same result set like

SELECT  `photos`.`id` 
FROM  `photos` 
LEFT JOIN  `friends` ON (  `friends`.`friend_id` =  `photos`.`user_id` ) 
WHERE  `friends`.`user_id` =1
OR  `photos`.`user_id` =1
LIMIT 0 , 30

Which obviously gets the wrong results because of the left join I get a result for every friend I have

I’m thinking I need to inner join an aliased table for the OR clause or something but can’t figure it out.

Answer 1

What if just use UNION for two your first queries:

SELECT `photos`.`id` 
   FROM `photos` 
        LEFT JOIN `friends` ON (`friends`.`friend_id` = `photos`.`user_id`) 
   WHERE `friends`.`user_id` = 1
union all 
SELECT `photos`.`id` FROM `photos` WHERE `photos`.`user_id` = 1

If you do not want to use UNION then

SELECT `photos`.`id` 
   FROM `photos` where `photos`.`user_id`=1
                   or `photos`.`user_id` 
                       in (select `friends`.`friend_id` from `friends`
                                             where `friends`.`user_id` = 1)