Question

我有3张不同的桌子

1. Table Business
ID, Name, fk_Input, fk_Output

2. Table Input
Id, FK_Business_id, Name

3.
Id, FK_Business_id, Name

我在SQLFiddle上创建了一个数据库示例。

现在只想检查业务是否具有相同的output.name，就像其他一些Business具有Input.name并显示为结果，可以共享商业名称和资源。

这是一个更好理解的例子

1. Table Business
ID, Name, fk_Input, fk_Output

1, AdventureA, 1,1
2, BuinsnessB, 2,2
3, CompanyC,   3,3

2.Table Input
Id, FK_Business_id, Name
1, 1(AdventureA),coal
2, 1(AdventureA),Air
3, 2(BusinessB) ,Cooper
4, 2(BusinessB) ,Power
5, 3(CompanyC)  ,Wood

3.Table Output
Id, FK_Business_id, Name
1, 1(AdventureA), Power
2, 2(BusinessB) , Cooperbar     
3, 3(CompanyC)  , Power

结果应该是：

AdventureA has Power for BusinessB
CompanyC   has Power for BusinessB

或者换句话说就像这样

BusinessnameOutput, BusinessnameInput, NameInput, NameOutput

我试过了

SELECT DISTINCT Business.Name, Output.Name, Input.Name FROM Business, Input, Output 
WHERE Output.Name = Input.Name

但导致很多行没有任何意义

也尝试了

SELECT Business.Name, Input.Name, Output.Name 
FROM Unternehmen 
INNER JOIN Input ON Input.FK_Business_id,   = Business.ID 
INNER JOIN Output ON Output.FK_Business_id = Business.ID
WHERE Input.Name = Output.Name

但不会导致任何条目。

查询几乎正确的结果是

SELECT Business.Name, Input.Name, Output.Name FROM Business,Input, Output WHERE Input.Name = Output.Name GROUP BY Input.RessourceName

但它只显示一个Businessname，而不是两个同时具有相同输出的商业名称。

我不知道如何解决这个难题？任何人都有了想法，那会很棒。

Answer 1

您可以使用内部联接和适当的条件进行加入

select distinct concat( Business.Name, ' has ',  Output.Name, ' for ', Business2.name) 
from Business 
inner join Output on Business.fk_Output = Output.id
inner join Input on Input.name = Output.name
inner join Business as Business2 on Input.fk_business_id = Business2.id ;

http://sqlfiddle.com/#!9/de4efa/6

SQL查询如果两个条目相等，则从三个表中选择四个条目

1 个答案: