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Asked: 2026-05-16T21:23:38+00:00

I have a table with columns like these : idx | amount | usercol1

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I have a table with columns like these :

idx | amount | usercol1 | usercol2 | usercol3 | percentage1 | percentage2 | percentage3

Data is typically like this :

0   | 1500   | 1        | null     | null     | 100         | null        | null
1   | 3000   | 2        | 3        | null     | 50          | 50          | null

I would like to make a SUM() of every user’s amount.

Example :

  • user1= 1500*100/100 (amount*usercol1/100)
  • user2= 3000*50/100 (amount*usercol1/100)
  • user3= 3000*50/100 (amount*usercol2/100)

I tried UNION to no avail (did not sum the SUMs).

Is there a way to do this ? The problem being that it should GROUP BY the username (which I get with a LEFT OUTER JOIN usernames ON exampletable.usercol1=usernames.idx).

I know this is non standard and would be better with relations from another table. But I am not allowed to change the table structure.

Many many many thanks ! :=)

Hereby, an example that gives a wrong result (seems to give only results from the query in the middle)

( 
SELECT SUM(projects.amount * (projects.percentage1/100)) as totalproj, 
entities.idx as idx, 
COUNT(projects.idx) as numproj, 
entities.name 
 FROM projects 
 INNER JOIN entities ON projects.usercol1=entities.idx 
 WHERE projects.usercol1=entities.idx 
GROUP BY name ORDER BY totalproj DESC 
) 
UNION ALL
( 
SELECT SUM(projects.amount * (projects.percentage2/100)) as totalproj, 
entities.idx as idx, 
COUNT(projects.idx) as numproj, 
entities.name 
 FROM projects 
 INNER JOIN entities ON projects.usercol2=entities.idx 
 WHERE projects.usercol2=entities.idx 
GROUP BY name ORDER BY totalproj DESC 
) 
UNION ALL
( 
SELECT SUM(projects.amount * (projects.percentage3/100)) as totalproj, 
entities.idx as idx, 
COUNT(projects.idx) as numproj, 
entities.name 
 FROM projects 
 INNER JOIN entities ON projects.usercol3=entities.idx 
 WHERE projects.usercol3=entities.idx 
GROUP BY name ORDER BY totalproj DESC 
)
ORDER BY totalproj DESC 
LIMIT 10
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1 Answer

  1. Editorial Team

    You could use a derived table to simulate a first normal form table then join onto that.

    SELECT SUM(P.amount * (P.percentage/100)) as totalproj, 
       entities.idx as idx, 
       COUNT(P.idx) as numproj, 
       entities.name 
FROM 
(
SELECT idx, amount, usercol1 AS usercol, percentage1 AS percentage
FROM projects
UNION ALL
SELECT idx, amount, usercol2 AS usercol, percentage2 AS percentage
FROM projects
UNION ALL
SELECT idx, amount, usercol3 AS usercol, percentage3 AS percentage
FROM projects
) P
 INNER JOIN entities ON P.usercol=entities.idx 
 WHERE P.usercol=entities.idx 
 GROUP BY name 
 ORDER BY totalproj DESC
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