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100 lines
3.0 KiB
HTML
100 lines
3.0 KiB
HTML
<p>Table: <code>Users</code></p>
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<pre>
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+----------------+---------+
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| Column Name | Type |
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+----------------+---------+
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| user_id | int |
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| join_date | date |
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| favorite_brand | varchar |
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+----------------+---------+
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user_id is the primary key of this table.
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This table has the info of the users of an online shopping website where users can sell and buy items.
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</pre>
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<p> </p>
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<p>Table: <code>Orders</code></p>
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<pre>
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+---------------+---------+
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| Column Name | Type |
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+---------------+---------+
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| order_id | int |
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| order_date | date |
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| item_id | int |
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| buyer_id | int |
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| seller_id | int |
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+---------------+---------+
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order_id is the primary key of this table.
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item_id is a foreign key to the Items table.
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buyer_id and seller_id are foreign keys to the Users table.
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</pre>
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<p> </p>
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<p>Table: <code>Items</code></p>
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<pre>
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+---------------+---------+
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| Column Name | Type |
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+---------------+---------+
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| item_id | int |
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| item_brand | varchar |
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+---------------+---------+
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item_id is the primary key of this table.
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</pre>
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<p> </p>
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<p>Write an SQL query to find for each user, the join date and the number of orders they made as a buyer in <code>2019</code>.</p>
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<p>Return the result table in <strong>any order</strong>.</p>
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<p>The query result format is in the following example.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<pre>
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<strong>Input:</strong>
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Users table:
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+---------+------------+----------------+
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| user_id | join_date | favorite_brand |
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+---------+------------+----------------+
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| 1 | 2018-01-01 | Lenovo |
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| 2 | 2018-02-09 | Samsung |
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| 3 | 2018-01-19 | LG |
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| 4 | 2018-05-21 | HP |
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+---------+------------+----------------+
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Orders table:
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+----------+------------+---------+----------+-----------+
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| order_id | order_date | item_id | buyer_id | seller_id |
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+----------+------------+---------+----------+-----------+
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| 1 | 2019-08-01 | 4 | 1 | 2 |
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| 2 | 2018-08-02 | 2 | 1 | 3 |
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| 3 | 2019-08-03 | 3 | 2 | 3 |
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| 4 | 2018-08-04 | 1 | 4 | 2 |
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| 5 | 2018-08-04 | 1 | 3 | 4 |
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| 6 | 2019-08-05 | 2 | 2 | 4 |
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+----------+------------+---------+----------+-----------+
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Items table:
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+---------+------------+
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| item_id | item_brand |
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+---------+------------+
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| 1 | Samsung |
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| 2 | Lenovo |
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| 3 | LG |
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| 4 | HP |
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+---------+------------+
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<strong>Output:</strong>
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+-----------+------------+----------------+
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| buyer_id | join_date | orders_in_2019 |
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+-----------+------------+----------------+
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| 1 | 2018-01-01 | 1 |
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| 2 | 2018-02-09 | 2 |
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| 3 | 2018-01-19 | 0 |
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| 4 | 2018-05-21 | 0 |
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+-----------+------------+----------------+
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</pre>
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