[Leetcode SQL] Customers Who Never Order, leetcodecustomers

Source: Internet
Author: User

[Leetcode SQL] Customers Who Never Order, leetcodecustomers

Suppose that a website contains two tables,MERsTable andOrdersTable. Write a SQL query to find all customers who never order anything.

Table:MERs.

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

The solution is as follows:

Select name as Customersfrom Customers a left join Orders B on a. Id = B. CustomerIdwhere CustomerId is null


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