SQL RIGHT JOIN 关键字
发布于 2015-08-23 10:51:50 | 255 次阅读 | 评论: 0 | 来源: 网络整理
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。
SQL RIGHT JOIN 语法
SELECT column_name(s)
FROM table1
RIGHT JOIN table2
ON table1.column_name=table2.column_name;
FROM table1
RIGHT JOIN table2
ON table1.column_name=table2.column_name;
或：
SELECT column_name(s)
FROM table1
RIGHT OUTER JOIN table2
ON table1.column_name=table2.column_name;
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。
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.... |
SQL RIGHT JOIN 实例
下面的 SQL 语句将返回所有员工及他们处理的订单：
实例
SELECT Orders.OrderID, Employees.FirstName
FROM Orders
RIGHT JOIN Employees
ON Orders.EmployeeID=Employees.EmployeeID
ORDER BY Orders.OrderID;
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。