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Dokumen ini menggunakan Manual laman web PHP Cina Lepaskan
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。
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。
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:
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。