183-CustomersWhoNeverOrder.sql

-- 183. Customers Who Never Order
-- Table: Customers
--
-- +-------------+---------+
-- | 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.
--  
-- Table: Orders
--
-- +-------------+------+
-- | 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.
--  
-- Write an SQL query to report all customers who never order anything.
-- Return the result table in any order.
-- The query result format is in the following example.
--
-- Example 1:
--
-- Input:
-- Customers table:
-- +----+-------+
-- | id | name  |
-- +----+-------+
-- | 1  | Joe   |
-- | 2  | Henry |
-- | 3  | Sam   |
-- | 4  | Max   |
-- +----+-------+
-- Orders table:
-- +----+------------+
-- | id | customerId |
-- +----+------------+
-- | 1  | 3          |
-- | 2  | 1          |
-- +----+------------+
-- Output:
-- +-----------+
-- | Customers |
-- +-----------+
-- | Henry     |
-- | Max       |
-- +-----------+
--
-- Write your MySQL query statement below
SELECT
    name AS Customers
FROM
    Customers
WHERE
    id NOT IN (
        SELECT
            customerId
        FROM
            Orders
    )