180606_Combine&Find
2018-06-06 本文已影响0人
郑磊_4135
合并后，查找未出现的ID
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.
| Id | Name |
|---|---|
| 1 | Joe |
| 2 | Henry |
| 3 | Sam |
| 4 | Max |
Table: Customers.
| Id | Name |
|---|---|
| 1 | Joe |
| 2 | Henry |
| 3 | Sam |
| 4 | Max |
| Id | CustomerId |
|---|---|
| 1 | 3 |
| 2 | 1 |
Table: Orders.
| Id | CustomerId |
|---|---|
| 1 | 3 |
| 2 | 1 |
| Customers |
|---|
| Henry |
| Max |
Using the above tables as example, return the following:
| Customers |
|---|
| Henry |
| Max |
SELECT C.Name as Customers
FROM Customers C
WHERE C.Id NOT IN (SELECT CustomerId
FROM Orders);
