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183. Customers Who Never Order

183. Customers Who Never Order

作者: 无敌的肉包 | 来源:发表于2018-06-07 12:00 被阅读0次

    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       |
    +-----------+
    

    Solution:

    SELECT Name as 'Customers'
    FROM Customers 
    WHERE Customers.Id NOT IN(
    SELECT CustomerId
    FROM Orders)
    

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