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       |

+-----------+

　 solutions:

SELECT A.Name from Customers A

LEFT JOIN Orders B on  a.Id = B.CustomerId

WHERE b.CustomerId is NULL

SELECT A.Name from Customers A

WHERE NOT EXISTS (SELECT 1 FROM Orders B WHERE A.Id = B.CustomerId)

SELECT A.Name from Customers A

WHERE A.Id NOT IN (SELECT B.CustomerId from Orders B)

select c.Name from Customers c
where (select count(*) from Orders o where o.customerId=c.id)=0