DELOITTE SQL Interview Question | SQL Intermediate Question 19

Question - Find the products whose sales are increasing every year.
CREATE TABLE products (
product_id INT PRIMARY KEY,
product_name VARCHAR(50),
category VARCHAR(50)
);
INSERT INTO products (product_id, product_name, category) VALUES
(1, 'Laptops', 'Electronics'),
(2, 'Jeans', 'Clothing'),
(3, 'Chairs', 'Home Appliances');
CREATE TABLE sales (
product_id INT,
year INT,
total_sales_revenue DECIMAL(10, 2),
PRIMARY KEY (product_id, year),
FOREIGN KEY (product_id) REFERENCES products(product_id)
);
INSERT INTO sales (product_id, year, total_sales_revenue) VALUES
(1, 2019, 1000.00),
(1, 2020, 1200.00),
(1, 2021, 1100.00),
(2, 2019, 500.00),
(2, 2020, 600.00),
(2, 2021, 900.00),
(3, 2019, 300.00),
(3, 2020, 450.00),
(3, 2021, 400.00);
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[@ardsha]

we can also achive this by using following :
with cte as (
select *,
LEAD(total_sales_revenue,1) over (partition by product_id order by year) as nxt_rev,
LEAD(total_sales_revenue,2) over (partition by product_id order by year) as nxtnext_rev
from sales)
select p.product_id,p.product_name,p.category from cte c
join products p
on c.product_id=p.product_id
where nxtnext_rev>nxt_rev and nxt_rev>total_sales_revenue

[@vijaygupta7059]

my solution on MSSQL DB:
with cte as
(
Select *
,case when total_sales_revenue< lead(total_sales_revenue,1, total_sales_revenue+1)over(partition by product_id order by year) then 1 else null end as new
from sales
), sales_cte as(
Select * from sales where product_id not in (select product_id from cte where new is null)
)
select products.* from sales_cte inner join products on sales_cte.product_id = products.product_id
group by products.product_id, products.product_name, products.category

[@saicharan5846]

First view

[@shryk0s963]

with cte as (select *,(lead(total_sales_revenue) over (partition by product_id order by year)-total_sales_revenue)as x from sales)
select distinct c.product_id,p.product_name from cte c inner join productss p on c.product_id=p.product_id where c.product_id not in (select product_id from cte where x

[@suvadipkundu152]

can we do it without using a CTE? i suspect we can , though unlikely to be optimal, thoughts??

[@Code-Con]

Try it out

[@chandanpatra1053]

Hi bro,
can you please send me the solution for this question
create table brands
(
Year int,
Brand varchar(20),
Amount int
)
insert into brands values (2018, 'Apple', 45000);
insert into brands values (2019, 'Apple', 35000);
insert into brands values (2020, 'Apple', 75000);
insert into brands values (2018, 'Samsung', 15000);
insert into brands values (2019, 'Samsung', 20000);
insert into brands values (2020, 'Samsung', 25000);
insert into brands values (2018, 'Nokia', 21000);
insert into brands values (2019, 'Nokia', 17000);
insert into brands values (2020, 'Nokia', 14000);
Write a query to fetch the records of brands whose Revenue is increasing every year?
Altough the question you have solved is similar. But differrence is it is a single table and don't have id.
I tried to solve the approach you have said. But I can't resolve it. Please make a video or help me in the solution..

[@Code-Con]

ok will make a video on this soon

[@anime_763]

My solution
with cte as (
SELECT *
,LEAD(total_sales1_revenue,1) OVER(PARTITION BY product_id ORDER BY year) Year1
,LEAD(total_sales1_revenue,2) OVER(PARTITION BY product_id ORDER BY year) year2
,ROW_NUMBER() OVER (PARTITION BY product_id ORDER BY year) as RW
FROM sales1
)
,cte2 as(
SELECT *,
CASE WHEN (total_sales1_revenue < Year1 ) AND (Year1 < Year2) THEN 1 ELSE 0 END flag
FROM cte
WHERE RW = 1
)
SELECT P.*
FROM products1 P
JOIN cte2 C ON
P.product_id=C.product_id
WHERE C.flag = 1

[@chandanpatra1053]

bro why don't you explain first logic in excel then jump to sql editor to write. can you explain the logic behind total_sales_revenue>nxt>rvn in excel. because there are for product_id 2 every row doesn't satisfy the codition. but how it is working I didn't get it. Please explain in excel first. I have already given feedback related to you previously.

[@Code-Con]

It should not satisfy the condition, i am selecting those ids that are not satisfying the condition caz total_sales_revenue>nxt_rvn means next year revenue is less which goes against the condition in the question, so we will not consider those ids hence i have used "not in" in where clause.
I hope it's clear now. and i will try to first show in excel the move to editor in coming videos.