LeetCode Hard 1479 'Sales by Day of the Week' Amazon Interview SQL Question with Explanation

In this video I solve and explain a hard difficulty leetcode SQL question using MySQL query. This question has been asked in Apple, Facebook, Amazon, Google, Adobe, Microsoft, Adobe interviews or what we popularly call FAANG interviews.
I explain the related concept as well. This question includes points to keep in mind to develop SQL queries.

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[cheerfulchai]

Hi! Can you share the solution on GitRepo as well?

[SchreiEs]

Another way of doing this with pivot function using SQL Server:

--Method 1

select
*
from
orderitem;

select
*
from
item;

with
combined as
(
select
item_category
, order_date
, datename(weekday, order_date) as weekday
, isnull(sum(quantity), 0) as total_orders
from
orderitem o
right join item i on o.item_id = i.item_id
group by
item_category
, order_date
)

, orders as
(
select
item_category as category
, weekday
, sum(total_orders) as total_orders
from
combined
group by
item_category
, weekday
)

--select * from combined;
--select * from orders;

select
category as Category
, isnull([Monday],0) as Monday
, isnull([Tuesday],0) as Tuesday
, isnull([Wednesday],0) as Wednesday
, isnull([Thursday],0) as Thursday
, isnull([Friday],0) as Friday
, isnull([Saturday],0) as Saturday
, isnull([Sunday],0) as Sunday
from
orders
pivot
(
sum(total_orders)
for
weekday in
([Monday], [Tuesday], [Wednesday], [Thursday], [Friday], [Saturday], [Sunday])
) as pvt
order by
category;