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  • 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       |
    +-----------+


    查找所有从不订购任何东西的客户。

    MySQL(821ms):
    1 # Write your MySQL query statement below
    2 SELECT Name AS Customers
    3 FROM Customers
    4 WHERE Id NOT IN (SELECT CustomerId  
    5                  FROM Orders) ;
    MySQL(803ms):  左外连接
    1 # Write your MySQL query statement below
    2 SELECT C.Name AS Customers
    3 FROM Customers AS C LEFT JOIN Orders AS O
    4   ON C.Id = O.CustomerId
    5 WHERE O.CustomerId IS NULL ;
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  • 原文地址:https://www.cnblogs.com/mengchunchen/p/8317800.html
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