Question

I will present my table structures first (only relevant fields will be mentioned)

/* The table Users */

user_id | user_name | user_registration_date
1       | USER1     | 19/09/2010
2       | USER2     | 20/09/2010


/* The table Levels_Completed */

user_id | level_id
1       | 1
1       | 2
2       | 1

I would like to display a scoreboard. The first user on the list, will be the one with the highest count of levels he completed.
For the example above, USER1 will be displayed above USER2.

I want to receive the next data:

user_id, user_name, user_registration_date, COUNT(level_id rows) AS score

Ordered by the count of score, for each SQL row I receive.
Example:

1 | USER1 | 19/09/2010 | 2
2 | USER2 | 20/09/2010 | 1

I know how to use INNER JOIN, but I think the counting and ordering are above my current level. Help please?

Answer 1

SELECT Users.user_id, user_name, user_registration_date, COUNT(level_id) AS score
FROM Users INNER JOIN Levels_Completed ON Users.user_id = Levels_Completed.user_id
GROUP BY Users.user_id, user_name, user_registration_date