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SQL RIGHT JOIN 关键字

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;

或:

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。

SQL RIGHT 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:

OrderIDCustomerIDEmployeeIDOrderDateShipperID
10308271996-09-183
103093731996-09-191
103107781996-09-202

选自 "Employees" 表的数据:

EmployeeIDLastNameFirstNameBirthDatePhotoNotes
1DavolioNancy12/8/1968EmpID1.picEducation includes a BA in psychology.....
2FullerAndrew2/19/1952EmpID2.picAndrew received his BTS commercial and....
3LeverlingJanet8/30/1963EmpID3.picJanet 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;

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。