1479-sales-by-day-of-the-week.sql

# Write your MySQL query statement below
SELECT i.item_category AS Category,
    SUM(CASE WHEN DAYOFWEEK(o.order_date) = 2 THEN quantity ELSE 0 END) AS Monday,
    SUM(CASE WHEN DAYOFWEEK(o.order_date) = 3 THEN quantity ELSE 0 END) AS Tuesday,
    SUM(CASE WHEN DAYOFWEEK(o.order_date) = 4 THEN quantity ELSE 0 END) AS Wednesday,
    SUM(CASE WHEN DAYOFWEEK(o.order_date) = 5 THEN quantity ELSE 0 END) AS Thursday,
    SUM(CASE WHEN DAYOFWEEK(o.order_date) = 6 THEN quantity ELSE 0 END) AS Friday,
    SUM(CASE WHEN DAYOFWEEK(o.order_date) = 7 THEN quantity ELSE 0 END) AS Saturday,
    SUM(CASE WHEN DAYOFWEEK(o.order_date) = 1 THEN quantity ELSE 0 END) AS Sunday
FROM Items i
LEFT JOIN Orders o
ON i.item_id = o.item_id
GROUP BY i.item_category
ORDER BY i.item_category;