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leetcode/problem/customers-who-never-order.html

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+<p>Table: <code>Customers</code></p>
+
+<pre>
++-------------+---------+
+| Column Name | Type    |
++-------------+---------+
+| id          | int     |
+| name        | varchar |
++-------------+---------+
+id is the primary key column for this table.
+Each row of this table indicates the ID and name of a customer.
+</pre>
+
+<p>&nbsp;</p>
+
+<p>Table: <code>Orders</code></p>
+
+<pre>
++-------------+------+
+| Column Name | Type |
++-------------+------+
+| id          | int  |
+| customerId  | int  |
++-------------+------+
+id is the primary key column for this table.
+customerId is a foreign key of the ID from the Customers table.
+Each row of this table indicates the ID of an order and the ID of the customer who ordered it.
+</pre>
+
+<p>&nbsp;</p>
+
+<p>Write an SQL query to report all customers who never order anything.</p>
+
+<p>Return the result table in <strong>any order</strong>.</p>
+
+<p>The query result format is in the following example.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> 
+Customers table:
++----+-------+
+| id | name  |
++----+-------+
+| 1  | Joe   |
+| 2  | Henry |
+| 3  | Sam   |
+| 4  | Max   |
++----+-------+
+Orders table:
++----+------------+
+| id | customerId |
++----+------------+
+| 1  | 3          |
+| 2  | 1          |
++----+------------+
+<strong>Output:</strong> 
++-----------+
+| Customers |
++-----------+
+| Henry     |
+| Max       |
++-----------+
+</pre>