Leetcode :: Algorithms :: Customers Who Never Order Solution

Author: Ravi-VL

databases/customers_who_never_order/Solution.sql

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+/*
+Customers Who Never Order
+
+Problem Statement:
+
+Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything.
+
+Table: Customers.
+
+	+----+-------+
+	| Id | Name  |
+	+----+-------+
+	| 1  | Joe   |
+	| 2  | Henry |
+	| 3  | Sam   |
+	| 4  | Max   |
+	+----+-------+
+
+Table: Orders.
+
+	+----+------------+
+	| Id | CustomerId |
+	+----+------------+
+	| 1  | 3          |
+	| 2  | 1          |
+	+----+------------+
+
+Using the above tables as example, return the following:
+
+	+-----------+
+	| Customers |
+	+-----------+
+	| Henry     |
+	| Max       |
+	+-----------+
+
+*/
+
+/* Difficulty Level -- Easy*/
+
+select Customers.Name as 'Customers' 
+from Customers
+where Customers.Id not in 
+(
+    select CustomerId from Orders
+);
+
+