SQL: derivated table

lets_derivate.sql

SELECT 
    AVG(count)
FROM # here the derivate table comes
    (SELECT 
        COUNT(*) AS count
    FROM
        `bets`
    WHERE
        state = 'pending'
    GROUP BY user_id
    ) b; # Every derived table must have its own alias
    
# Usage of the derivate table let us compute the AVG of the grouped sql count.