带有 3 个表的 SQL 内连接？

Question

我正在尝试在一个视图中加入 3 个表；情况如下：

我有一张表格，其中包含申请住在这所大学校园的学生的信息。我有另一个表格，列出了每个学生的 Hall Preferences（其中 3 个）。但是这些偏好中的每一个都只是一个ID号，并且ID号在第三张表中有一个对应的Hall Name（不是设计这个数据库......）。

差不多，我在桌子上有INNER JOIN 他们的偏好和信息，结果类似于...

 John Doe | 923423 | Incoming Student | 005

005 将是 HallID。所以现在我想将HallID 匹配到第三个表，其中该表包含HallID 和HallName。

差不多了，我希望我的结果是......

 John Doe | 923423 | Incoming Student | Foley Hall <---(INSTEAD OF 005)

这是我目前拥有的：

SELECT
  s.StudentID, s.FName, 
  s.LName, s.Gender, s.BirthDate, s.Email, 
  r.HallPref1, r.HallPref2, r.HallPref3
FROM
  dbo.StudentSignUp AS s 
  INNER JOIN RoomSignUp.dbo.Incoming_Applications_Current AS r 
    ON s.StudentID = r.StudentID 
  INNER JOIN HallData.dbo.Halls AS h 
    ON r.HallPref1 = h.HallID

Answer 1

如果您有 3 个具有相同 ID 的表要加入，我想应该是这样的：

SELECT * FROM table1 a
JOIN table2 b ON a.ID = b.ID
JOIN table3 c ON a.ID = c.ID

只需将* 替换为您想从表格中获取的内容即可。

Answer 2

您只需要第二个内部联接，将您现在拥有的ID Number 链接到第三个表的ID Number。之后，将 ID Number 替换为 Hall Name 和瞧 :)

Answer 3

您可以执行以下操作（我猜是表格字段等）

SELECT s.studentname
    , s.studentid
    , s.studentdesc
    , h.hallname
FROM students s
INNER JOIN hallprefs hp
    on s.studentid = hp.studentid
INNER JOIN halls h
    on hp.hallid = h.hallid

根据您对多个大厅的要求，您可以这样做。您只需为每个房间 pref id 多次加入 Hall 表：

SELECT     s.StudentID
    , s.FName
    , s.LName
    , s.Gender
    , s.BirthDate
    , s.Email
    , r.HallPref1
    , h1.hallName as Pref1HallName
    , r.HallPref2 
    , h2.hallName as Pref2HallName
    , r.HallPref3
    , h3.hallName as Pref3HallName
FROM  dbo.StudentSignUp AS s 
INNER JOIN RoomSignUp.dbo.Incoming_Applications_Current AS r 
    ON s.StudentID = r.StudentID 
INNER JOIN HallData.dbo.Halls AS h1 
    ON r.HallPref1 = h1.HallID
INNER JOIN HallData.dbo.Halls AS h2
    ON r.HallPref2 = h2.HallID
INNER JOIN HallData.dbo.Halls AS h3
    ON r.HallPref3 = h3.HallID

Answer 4

SELECT column_Name1,column_name2,......
  From tbl_name1,tbl_name2,tbl_name3
  where tbl_name1.column_name = tbl_name2.column_name 
  and tbl_name2.column_name = tbl_name3.column_name

Answer 5

这是对具有相同 id 的连接 3 表的正确查询**

select a.empname,a.empsalary,b.workstatus,b.bonus,c.dateofbirth from employee a, Report b,birth c where a.empid=b.empid and a.empid=c.empid and b.empid='103';

员工第一张桌子。 报告第二张表。 出生第三桌

Answer 6

select empid,empname,managename,[Management ],cityname  
from employees inner join Managment  
on employees.manageid = Managment.ManageId     
inner join CITY on employees.Cityid=CITY.CityId


id name  managename  managment  cityname
----------------------------------------
1  islam   hamza       it        cairo

Answer 7

SELECT table1.col,table2.col,table3.col 
FROM table1 
INNER JOIN 
(table2 INNER JOIN table3 
ON table3.id=table2.id) 
ON table1.id(f-key)=table2.id
AND //add any additional filters HERE

Answer 8

SELECT * 
FROM 
    PersonAddress a, 
    Person b,
    PersonAdmin c
WHERE a.addressid LIKE '97%' 
    AND b.lastname LIKE 'test%'
    AND b.genderid IS NOT NULL
    AND a.partyid = c.partyid 
    AND b.partyid = c.partyid;

Answer 9

SELECT 
A.P_NAME AS [INDIVIDUAL NAME],B.F_DETAIL AS [INDIVIDUAL FEATURE],C.PL_PLACE AS [INDIVIDUAL LOCATION]
FROM 
[dbo].[PEOPLE] A
INNER JOIN 
[dbo].[FEATURE] B ON A.P_FEATURE = B.F_ID
INNER JOIN 
[dbo].[PEOPLE_LOCATION] C ON A.P_LOCATION = C.PL_ID

Answer 10

这个查询对你有用

Select b.id as 'id', u.id as 'freelancer_id', u.name as 
'free_lancer_name', p.user_id as 'project_owner', b.price as 
'bid_price', b.number_of_days as 'days' from User u, Project p, Bid b 
where b.user_id = u.id and b.project_id = p.id

Answer 11

有很多回应，但总的教训似乎是您可以在 where 子句中使用多个 JOINS； techonthenet.com（我的老板向我推荐了它，我就是这样找到它的）也有很好的 SQL 教程，如果你还有其他问题，你只是想试着弄清楚。

SELECT table1.column1
FROM table1
WHERE table1 > 0 (or whatever you want to specify)
INNER JOIN table1 
ON table1.column1 = table2.column1

Answer 12

select products.product_id, product_name, price, created_at, image_name, categories.category_id, category_name,brands.brand_id, brand_name 
FROM products INNER JOIN categories USING (category_id) INNER JOIN brands USING(brand_id)