-- 183. Customers Who Never Order
--
-- 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       |
-- +-----------+

-- # Write your MySQL query statement below

-- Solution 1
SELECT A.Name as Customers from Customers A
WHERE NOT EXISTS (SELECT 1 FROM Orders B WHERE A.Id = B.CustomerId)

-- Solution 2
SELECT A.Name as Customers from Customers A
LEFT JOIN Orders B on  a.Id = B.CustomerId
WHERE b.CustomerId is NULL

-- Solution 3
SELECT A.Name as Customers from Customers A
WHERE A.Id NOT IN (SELECT B.CustomerId from Orders B)