1098 added

Author: MaxineXiong

1098-Unpopular-Books/1098-Unpopular-Books.sql

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+----Solution to LeetCode Database question 1098: Unpopular Books
+
+WITH scopped_books AS
+(
+  SELECT book_id, name
+  FROM Books
+  WHERE available_from NOT BETWEEN DATE_ADD('2019-06-23', INTERVAL -1 MONTH) AND '2019-06-23'
+),
+orders_in_scope AS
+(
+  SELECT o.book_id, o.quantity
+  FROM Orders AS o
+  JOIN scopped_books AS sb
+  ON o.book_id = sb.book_id
+  WHERE o.dispatch_date BETWEEN DATE_ADD('2019-06-23', INTERVAL -1 YEAR) AND '2019-06-23'
+)
+
+SELECT sb.book_id, sb.name
+FROM scopped_books AS sb
+LEFT JOIN orders_in_scope AS os
+ON sb.book_id = os.book_id
+GROUP BY sb.book_id
+HAVING SUM(IFNULL(os.quantity, 0)) < 10

1098-Unpopular-Books/README.md

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+### 1098. Unpopular Books
+
+Table: `Books`
+
+```markdown
++----------------+----------+
+| Column Name    | Type     |
++----------------+----------+
+| book_id        | int      |
+| name           | varchar  |
+| available_from | int      |
++----------------+----------+
+book_id is the primary key of this table.
+```
+
+<br/>
+
+Table: `Orders`
+
+```markdown
++----------------+----------+
+| Column Name    | Type     |
++----------------+----------+
+| order_id       | int      |
+| book_id        | int      |
+| quantity       | int      |
+| dispatch_date  | date     |
++----------------+----------+
+order_id is the primary key of this table.
+book_id is a foreign key to the Books table.
+```
+
+<br/>
+
+Write an SQL query that reports the **books** that have sold **less than** `10 copies` in the last year, excluding books that have been available for less than one month from today. **Assume today is** `2019-06-23`.
+
+Return the return table in **any order**.
+
+The query result format is in the following example.
+
+<br/>
+
+**Example 1:**
+
+```markdown
+Books table:
++---------+---------------------+-----------------+
+| book_id | name                | available_from  |
++---------+---------------------+-----------------+
+| 1       | "Kalila And Demna"  | 2010-01-01      |
+| 2       | "28 Letters"        | 2012-05-12      |
+| 3       | "The Hobbit"        | 2019-06-10      |
+| 4       | "13 Reasons Why"    | 2019-06-01      |
+| 5       | "The Hunger Games"  | 2008-09-21      |
++---------+---------------------+-----------------+
+
+Books table:
++---------+---------+----------+-----------------+
+| book_id | book_id | quantity | dispatch_date   |
++---------+---------+----------+-----------------+
+| 1       | 1       | 2        | 2018-07-26      |
+| 2       | 1       | 1        | 2018-11-05      |
+| 3       | 3       | 8        | 2019-06-11      |
+| 4       | 4       | 6        | 2019-06-05      |
+| 5       | 4       | 5        | 2019-06-20      |
+| 6       | 5       | 9        | 2009-02-02      |
+| 7       | 5       | 8        | 2010-04-13      |
++---------+---------+----------+-----------------+
+
+output:
++---------+---------------------+
+| book_id | name                |
++---------+---------------------+
+| 1       | "Kalila And Demna"  |
+| 2       | "28 Letters"        |
+| 5       | "The Hunger Games"  |
++---------+---------------------+
+```
+
+<br/>
+
+Refer to **1098-Unpopular-Books.sql** for my solution.