需要帮助优化SQL查询

Question

I want to see all users which following me or another user.

I have got used 3 tables

users

• id
• username

user_follow

• id
• user_id
• follow_id
• date

images

• id
• user_id
• image

I tried to get username with last image uploaded and also I need my and followers status to see if I already follow them or no.

My query is written on Mysql :

SELECT 
          u.id AS user_id,
          u.username,
          i.image,
          t.id AS STATUS 
FROM
          users AS u 
          INNER JOIN (user_follow AS f) 
                    ON (u.id = f.user_id) 
          LEFT OUTER JOIN images i 
                    ON i.id = 
                    (SELECT 
                              b.id 
                    FROM
                              images AS b 
                    WHERE f.user_id = b.user_id 
                    ORDER BY b.id DESC 
                    LIMIT 1) 
          LEFT OUTER JOIN user_follow t 
                    ON t.id = 
                    (SELECT 
                              m.id 
                    FROM
                              user_follow m 
                    WHERE user_id = 3 
                              AND follow_id = u.id) 
WHERE f.follow_id = 7 
          AND f.user_id NOT IN (7, 3) 
GROUP BY f.user_id 

My user id - 3; I watch users who are following user with id - 7

And output is :

Array
(
    [0] => Array
        (
            [user_id] => 6
            [username] => 6666
            [image] => flw3utn9igiqh7dtt2o61ydf8_174.jpeg
            [status] => 226
        )

)

I think that my query is too heigh and I do not know how to simple check status and output 1 or 0 . Now I get a follow line id if "follow" and empty if no. Also I will be happy if you show me how to optimaize my query.

Answer 1

UVP - user who is viewing the page. FBV - User whose profile\\list of follower is getting viewed. Last col of below query will give 0 if UVP is not following FBV else 1 . It will be difficult to optimize the query 1) You want the row data in col (transpose){ first LOJ} 2) You have 2 tables where data might or might not be there {next 2 LOJ}

      select *,(case when (uf3.id is not null) then 'follow' else null end) aa 
  from users u  
    left outer join 
                (Select * from 
                 user_follow 
                 where user_id = <FVP>
                 and follow_id =<UVP>) uf3 on uf3.user_id = u.id  
    left outer join 
            (select * from images where user_id = <FBV> ORDER BY id DESC 
                LIMIT 1) i
     on i.user_id = u.id 
    left outer join 
                (Select * 
                 from user_follow 
                 where user_id =<FVP>  
                 and follow_id !=<UVP>)  uf  on uf.user_id = u.id  
    where u.id =<FBV>;