SQL-关联表查询（连表查询）

0、例如：select * from T1,T2     where T1.a=T2.a

1、连表查询 <=> join（inner join）内连接查询

数据源： 
Persion表： 

 

 Orders表： 

 

 

//使用连表查询
SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo 
FROM Persons,Orders 
WHERE Persons.Id_P = Orders.Id_P

//使用join查询
SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo
FROM Persons
INNER JOIN Orders
ON Persons.Id_P = Orders.Id_P
ORDER BY Persons.LastName

结果: