1158. Market Analysis I

https://leetcode.com/problems/market-analysis-i

Description

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.

Write an SQL query to find for each user, the join date and the number of orders they made as a buyer in 2019.

The query result format is in the following example:

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         |
+---------+------------+
Result table:
+-----------+------------+----------------+
| 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              |
+-----------+------------+----------------+

ac