sql (4) key and Join

新建表：

"Persons" 表：
Id_P LastName FirstName Address City
1 Adams John Oxford Street London
2 Bush George Fifth Avenue New York
3 Carter Thomas Changan Street Beijing

"Orders" 表：
Id_O OrderNo Id_P
1 77895 3
2 44678 3
3 22456 1
4 24562 1

查询语句：  key

SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo
FROM Persons, Orders
WHERE Persons.Id_P = Orders.Id_P

结果：

Carter Thomas 77895
Carter Thomas 44678
Adams John 22456
Adams John 24562

 

查询语句：  join

SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo
FROM Persons
INNER JOIN Orders
ON Persons.Id_P = Orders.Id_P

结果：

Carter Thomas 77895
Carter Thomas 44678
Adams John 22456
Adams John 24562

 

 

2018-04-26  11:33:41