Market Analysis I
Problem Statement - link #
SQL Schema
Create table If Not Exists Users (user_id int, join_date date, favorite_brand varchar(10))
Create table If Not Exists Orders (order_id int, order_date date, item_id int, buyer_id int, seller_id int)
Create table If Not Exists Items (item_id int, item_brand varchar(10))
Truncate table Users
insert into Users (user_id, join_date, favorite_brand) values ('1', '2018-01-01', 'Lenovo')
insert into Users (user_id, join_date, favorite_brand) values ('2', '2018-02-09', 'Samsung')
insert into Users (user_id, join_date, favorite_brand) values ('3', '2018-01-19', 'LG')
insert into Users (user_id, join_date, favorite_brand) values ('4', '2018-05-21', 'HP')
Truncate table Orders
insert into Orders (order_id, order_date, item_id, buyer_id, seller_id) values ('1', '2019-08-01', '4', '1', '2')
insert into Orders (order_id, order_date, item_id, buyer_id, seller_id) values ('2', '2018-08-02', '2', '1', '3')
insert into Orders (order_id, order_date, item_id, buyer_id, seller_id) values ('3', '2019-08-03', '3', '2', '3')
insert into Orders (order_id, order_date, item_id, buyer_id, seller_id) values ('4', '2018-08-04', '1', '4', '2')
insert into Orders (order_id, order_date, item_id, buyer_id, seller_id) values ('5', '2018-08-04', '1', '3', '4')
insert into Orders (order_id, order_date, item_id, buyer_id, seller_id) values ('6', '2019-08-05', '2', '2', '4')
Truncate table Items
insert into Items (item_id, item_brand) values ('1', 'Samsung')
insert into Items (item_id, item_brand) values ('2', 'Lenovo')
insert into Items (item_id, item_brand) values ('3', 'LG')
insert into Items (item_id, item_brand) values ('4', 'HP')
Table : Users
+----------------+---------+
| Column Name | Type |
+----------------+---------+
| user_id | int |
| join_date | date |
| favorite_brand | varchar |
+----------------+---------+
user_id is the primary key of this table.
This table has the info of the users of an online shopping website where users can sell and buy items.
Table : Orders
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| order_id | int |
| order_date | date |
| item_id | int |
| buyer_id | int |
| seller_id | int |
+---------------+---------+
order_id is the primary key of this table.
item_id is a foreign key to the Items table.
buyer_id and seller_id are foreign keys to the Users table.
Table : Items
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| item_id | int |
| item_brand | varchar |
+---------------+---------+
item_id is the primary key of this table.
Your Task:
Write an SQL query to find for each user, the join date and the number of orders they made as a buyer in 2019.
Return the result table in any order.
The query result format is in the following example.
Example #
Input:
Users table:
+---------+------------+----------------+
| user_id | join_date | favorite_brand |
+---------+------------+----------------+
| 1 | 2018-01-01 | Lenovo |
| 2 | 2018-02-09 | Samsung |
| 3 | 2018-01-19 | LG |
| 4 | 2018-05-21 | HP |
+---------+------------+----------------+
Orders table:
+----------+------------+---------+----------+-----------+
| order_id | order_date | item_id | buyer_id | seller_id |
+----------+------------+---------+----------+-----------+
| 1 | 2019-08-01 | 4 | 1 | 2 |
| 2 | 2018-08-02 | 2 | 1 | 3 |
| 3 | 2019-08-03 | 3 | 2 | 3 |
| 4 | 2018-08-04 | 1 | 4 | 2 |
| 5 | 2018-08-04 | 1 | 3 | 4 |
| 6 | 2019-08-05 | 2 | 2 | 4 |
+----------+------------+---------+----------+-----------+
Items table:
+---------+------------+
| item_id | item_brand |
+---------+------------+
| 1 | Samsung |
| 2 | Lenovo |
| 3 | LG |
| 4 | HP |
+---------+------------+
Output:
+-----------+------------+----------------+
| buyer_id | join_date | orders_in_2019 |
+-----------+------------+----------------+
| 1 | 2018-01-01 | 1 |
| 2 | 2018-02-09 | 2 |
| 3 | 2018-01-19 | 0 |
| 4 | 2018-05-21 | 0 |
+-----------+------------+----------------+
Solutions #
-- Write your T-SQL query statement below
select u.user_id as "buyer_id", u.join_date,
ifnull(count(order_date),0) as "orders_in_2019"
from users u left join orders o
on u.user_id = o.buyer_id
and year(o.order_date)='2019'
group by u.user_id
;