Question

I have the follow query:

SELECT `peers`.uid, `user`.userid FROM `peers`, `user` WHERE `user`.userid = `peers`.uid

the FF. is the result of the query

userid,uid
1,1
1,1
1,1
3,3
96,96
96,96

To update the result of that, I have the ff query setup:

UPDATE `user`
   INNER JOIN (    
   SELECT `peers`.uid, `user`.userid FROM `peers`, `user` WHERE `user`.userid = `peers`.uid
       ) AS my_current_select ON `user`.userid = my_current_select.userid
   SET `user`.credits = `user`.credits + 0.25

However, the update query update only 3 times, each plus once 0.25 credits into userID 1,3,96

This is not what I want. I want to uniquely add 0.25 credits into each row result of the query.
For example:

UID 1: UID1.credit = UID1.credit + 0.25 * 3 
UID 3: UID3.credit = UID3.credit + 0.25 * 1 
UID 3: UID96.credit = UID96.credit + 0.25 * 2

How can I achieve this result?

Answer 1

Perhaps change your inner query to:

SELECT `user`.userid, COUNT(`peers`.uid) as count 
FROM `peers`, `user` 
WHERE `user`.userid = `peers`.uid 
GROUP BY `user`.userid

to get:

userid,count
1,3
3,1
96,2

And then in your master query do:

UPDATE `user`
   INNER JOIN (    
   SELECT `user`.userid, COUNT(`peers`.uid) as count 
    FROM `peers`, `user` 
    WHERE `user`.userid = `peers`.uid 
    GROUP BY `user`.userid
       ) AS my_current_select ON `user`.userid = my_current_select.userid
   SET `user`.credits = `user`.credits + 0.25*my_current_select.count