Question

What one query can produce table_c?

I have three columns: day, person, and revenue_per_person. Right now I have to use two queries since I lose ‘person’ when producing table_b.

table_a uses all three columns:

SELECT day, person, revenue_per_person
FROM purchase_table
GROUP BY day, person

table_b uses only two columns due to AVG() and GROUP BY:

SELECT day, AVG(revenue) as avg_revenue
FROM purchase_table
GROUP BY day

table_c created from table_a and table_b:

SELECT 
   CASE 
   WHEN revenue_per_person > avg_revenue THEN 'big spender'
   ELSE 'small spender'
   END as spending_bucket
FROM ????

Answer 1

Maybe this could help, try this one

SELECT a.day,
    CASE 
        WHEN a.revenue_per_person > b.avg_revenue THEN 'big spender'
        ELSE 'small spender'
   END as spending_bucket
FROM
    (
        SELECT day, person, AVG(revenue) revenue_per_person
        FROM purchase_table
        GROUP BY day, person
    ) a INNER JOIN
    (
        SELECT day, AVG(revenue) as avg_revenue
        FROM purchase_table
        GROUP BY day
    ) b ON a.day = b.day