Question

I am trying to create an SQL statement that will essentially calculate points due to a variety of conditions. For example, I have tables: users, followers, pictures

followers and pictures have a user_id, and users has a column called “about”

I want to do some sort of select where I get the sum of:

1) If users.about is not empty, that is worth 100 points

2) If the user owns at least one pictures.type = “something”, that is worth 50 points

3) For every follower that is associated with that user, give 20 points each

So this SQL statement should select the sum of those three calculations. After, I want to use this SQL to create a view that essentially lists the user_id and its associated score.

I have tried various permutations but nothing is working. How would I do this? Thanks!

Answer 1

Here is one way:

SELECT sum(points) FROM (
  SELECT 100 points FROM users WHERE about <> '' AND user_id = ####
  UNION
  SELECT 50 points FROM users WHERE EXISTS (SELECT * FROM pictures WHERE user_id = ####)
  UNION
  SELECT 20 points FROM followers WHERE user_id = ####
)

Here is a second way:

SELECT IF(about <> '', 100, 0)
     + IF(EXISTS (SELECT * FROM pictures WHERE pictures.user_id = users.user_id), 50, 0)
     + (SELECT SUM(20) FROM followers WHERE followers.user_id = users.user_id) points
FROM users
WHERE user_id = ####