将两个MYSQL查询列结果合并为一个，以在ORDER BY中使用

Question

I have two queries to get user coins and gems value. i can get each field value as separately but i want them together as addition value.. (coins+gems) values to use in ORDER BY

Using this SQL query i can get coins field values...

SELECT user_id, meta_value as total_coins FROM wp_usermeta WHERE meta_key = '_coin' AND meta_value > 0 ORDER BY meta_value+0 DESC LIMIT 0,10

Coins Query Result

And using this to get gems field values...

SELECT user_id, meta_value as total_gems FROM wp_usermeta WHERE meta_key = '_gems' AND meta_value > 0 ORDER BY meta_value+0 DESC LIMIT 0,10

Gems Query Result

What i want is get _coin field value and then for that user_id get _gem field value and then addition those two values in one... like 690+21 = 711 as total_points.. Something like this..

`SELECT ( 

    SELECT meta_value FROM `wp_usermeta` as ue1

    WHERE meta_key = '_coin' AND meta_value > 0 ORDER BY meta_value+0 DESC LIMIT 0,50

) AS coins,
( 

    SELECT meta_value FROM `wp_usermeta` as ue2 

    WHERE ue2.user_id = ue1.user_id AND meta_key = '_gem' AND meta_value > 0 ORDER BY meta_value+0 DESC LIMIT 0,50

) AS gems,

coins+gems AS total_points

FROM wp_usermeta

ORDER BY total_points LIMIT 0, 50`

i know this SQL is not correct and that's why i need help.. please help me with this to correct this SQL

Answer 1

Instead of several subquery you should use a join the same table and repeat the code for addition

  SELECT ue1.meta_value coins , ue2.meta_value gems
       , ue1.meta_value + ue2.meta_value total_points
  FROM `wp_usermeta` as ue1
  INNER JOIN `wp_usermeta` as ue2 ON ue1.user ue2.user_id = ue1.user_id
      AND ue1.meta_key = '_coin' 
        AND ue2. meta_key = '_gem'
  WHERE ue1.meta_value > 0 
  AND   ue2.meta_value > 0 
  ORDER BY total_points LIMIT 0, 50