SQL RIGHT JOIN 关键字

RIGHT JOIN 关键字从右表（table2）返回所有的行，即使左表（table1）中没有匹配。如果左表中没有匹配，则结果为 NULL。

## 语法

```sql
SELECT column_name(s)
FROM table1
RIGHT JOIN table2
ON table1.column_name=table2.column_name;
```

或：

```sql
SELECT column_name(s)
FROM table1
RIGHT OUTER JOIN table2
ON table1.column_name=table2.column_name;
```

> 注释：在某些数据库中，RIGHT JOIN 称为 RIGHT OUTER JOIN。

## 实例

### 演示数据库

在本教程中，我们将使用众所周知的 Northwind 样本数据库。

下面是选自 "Orders" 表的数据：

| OrderID | CustomerID | EmployeeID | OrderDate | ShipperID |
| --- | --- | --- | --- | --- |
| 10308 | 2 | 7 | 1996-09-18 | 3 |
| 10309 | 37 | 3 | 1996-09-19 | 1 |
| 10310 | 77 | 8 | 1996-09-20 | 2 |

选自 "Employees" 表的数据：

| EmployeeID | LastName | FirstName | BirthDate | Photo | Notes |
| --- | --- | --- | --- | --- | --- |
| 1 | Davolio | Nancy | 12/8/1968 | EmpID1.pic | Education includes a BA in psychology..... |
| 2 | Fuller | Andrew | 2/19/1952 | EmpID2.pic | Andrew received his BTS commercial and.... |
| 3 | Leverling | Janet | 8/30/1963 | EmpID3.pic | Janet has a BS degree in chemistry.... |

下面的 SQL 语句将返回所有员工及他们处理的订单：

```sql

SELECT Orders.OrderID, Employees.FirstName
FROM Orders
RIGHT JOIN Employees
ON Orders.EmployeeID=Employees.EmployeeID
ORDER BY Orders.OrderID;
```

> 注释：RIGHT JOIN 关键字从右表（Employees）返回所有的行，即使左表（Orders）中没有匹配。