[英]how to join three tables and retrieve selected columns from the three tables and in oracle?
我有3张桌子。 电影院,订票和顾客
create table cinema
(
c_id int,
location varchar(10)
)
insert into cinema values(1,'New York');
insert into cinema values(2,'London');
insert into cinema values(3,'Paris');
create table booking
(
c_id int,
cust_id int
)
insert into booking values(1,10);
insert into booking values(2,11);
insert into booking values(3,12);
insert into booking values(3,13);
insert into booking values(2,14);
create table customer
(
cust_id int,
cust_name varchar(10)
)
insert into customer values(10,'sam');
insert into customer values(11,'adrian');
insert into customer values(12,'mark');
insert into customer values(13,'jim');
insert into customer values(14,'tom');
我想选择尚未在巴黎预订的所有客户的客户ID(即cust_id),客户名称(cust_name)和位置(来自电影院表)。
我想要的是-
cust_id cust_name location
10 sam New York
11 adrian London
14 tom London
我尝试了很多。。。我的代码之一是-
SELECT customer.cust_id,customer.cust_name,
cinema.location as Location FROM booking,cinema,customer
WHERE booking.c_id=cinema.c_id AND location!='Paris';
它给了我15个结果..我想不出该怎么做..请帮助我。
在您的代码中,您没有加入booking
给customer
,这导致了您的问题。 我在这里使用显式联接而不是隐式联接。 尽管没有区别 ,但显式语法是标准的。
select cu.cust_id, cu.cust_name, ci.location
from cinema ci
join booking b
on ci.c_id = b.c_id
join customer cu
on b.cust_id = cu.cust_id
where ci.location <> 'Paris'
我不确定您的预订表的结构。 我希望有更多列,例如票数等。
您的WHERE statement
不是您想要的那么具体。 您需要一个与booking.cust_id to customer.cust_id
相匹配的条件:
WHERE booking.c_id = cinema.c_id
AND booking.cust_id = customer.cust_id
AND location != 'Paris'
现在,您正在为所有客户组合获取结果。
请参阅以下示例:
Select
businessuser.UserName,
businessuser.EmailAddress,
businessimages.ImgName,
featured_cart.FeaturedPlan,featured_cart.StartDate
From featured_cart
Inner Join businessimages on featured_cart.FeaturedProId = businessimages.IdBusinessImages
Inner Join businessuser on businessimages.UserId = businessuser.IdBusinessUser
and featured_cart.FeaturedType = "Featured Email"
3张桌子是:
这个例子工作正常...
MS SQL Server 2008:
select cust_id, cust_name, location
from customer c
inner join booking b
inner join location l
on c.cust_id = b.cust_id and b.c_id=l.c_id
复合联接联接四个表:
二手4桌
本示例可以100%起作用您可以在W3schools中尝试使用此方法-内部联接“尝试一下” SQL编辑器表来自W3schools编辑器。
查询:
Select Customers.CustomerName as Table1_Customer, Orders.EmployeeID as Table2_Employee, OrderDetails.Quantity as Table3_OrderDetails,Products.ProductName as Table4_Products
From Customers
INNER JOIN Orders
ON Customers.CustomerID = Orders.CustomerID
INNER JOIN OrderDetails
ON Orders.OrderID = OrderDetails.OrderID
INNER JOIN Products
ON OrderDetails.ProductID = Products.ProductID Order by EmployeeID;
你好,你可以这样使用join:
SQL
select customer.cust_id,customer.cust_name,cinema.location from cinema,customer,booking where cinema.c_id=booking.c_id and booking.cust_id=customer.cust_id and cinema.location not like 'paris';
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