在 SQL 中加入具有相同列的同一个表

Question

I have 3 tables, that the one of them is information center table assumed table 1.

Table1 as (tank information)

-----------------------------------------
Prikey   TankName
-----------------------------------------
24       Tank1
25       Tank2

Table2 as (source)

-----------------------------------------
 ID         Tank Source ID   Opotional
-----------------------------------------
 1           25               Source
 2           24               test
            etc

Table3 as (Destination)

---------------------------------------------------
Tank Destination ID     Opotional      ID Source
---------------------------------------------------
25                      Destination    1 
24                      Destination    2
etc

I would like to get the "tank name" in twice and display the "Source" and "destination" with match ID of 'Tank'. So both of them having Tank ID that I use on one query. I have tried joined but is crashed. Is it possible?

Hope the result is :

--------------------------------------------------------------------------------------------------
Source (tank Name)   |  Destination (Tank Name)  | opotional (source) | Opotional (Destination)
--------------------------------------------------------------------------------------------------

Answer 1

You just need to use aliases, Both on the tables that you join more than once (Table1) and on the fields that you return more than once (TankName, Optional).

Something like:

select Source.TankName as SourceTank, Destination.TankName as DestinationTank, 
       Table2.Optional as SourceOptional, Table3.Optional as DestionationOptional
from Table2
     inner join Table3 on Table3.ID = Table2.ID
     inner join Table1 as Source on Source.PriKey = Table2.TankID
     inner join Table1 as Destination on Destination.PriKey = Table3.TankID

Answer 2

SELECT [Table2].Opotional AS 'opotional (source)',
       [Table3].Opotional AS 'Opotional (Destination)',
       [Table1].TankName AS 'Source (tank Name)',
       t1.TankName AS 'Destination (Tank Name)'
FROM [Table2]
     INNER JOIN [Table3] ON Table3.[ID Source] = [Table2].[ID]
     INNER JOIN Table1 ON [Table2].[Tank Source ID] = [Table1].Prikey
     INNER JOIN Table1 t1 ON Table3.[Tank Destination ID] = t1.Prikey;

Answer 3

This query will help you to achieve the expected result..

select a.Tankname as [Source (tank Name)],
       a.Tankname as[Destination (Tank Name)],
       b.Optional as [Optional Source],
       c.Optional as [Optional Destination] 
from Table2 as b 
    join Table3 as c on b.ID = c.[ID Source] 
    join Table1 as a on c.[Tank Destination ID] = a.prikey

Answer 4

Try this:

DECLARE @tbl1 as TABLE(
    Prikey  INT,
    TankName VARCHAR(50)
)

DECLARE @tbl2 as TABLE(
   ID  INT,
   TankSourceID  INT,
   Opotional  VARCHAR(50)
)

DECLARE @tbl3 as TABLE(
   TankDestinationID  INT,
   Opotional VARCHAR(50),
   IDSource  INT
)

INSERT INTO @tbl1 VALUES(1,'Tank1')
INSERT INTO @tbl1 VALUES(2,'Tank2')
INSERT INTO @tbl1 VALUES(3,'Tank3')

INSERT INTO @tbl2 VALUES(1,1,'Source')
INSERT INTO @tbl2 VALUES(2,3,'Test')

INSERT INTO @tbl3 VALUES(1,'Destination1',1)
INSERT INTO @tbl3 VALUES(2,'Destination2',2)


SELECT
    T1.TankName AS 'Source',
    T1_2.TankName AS 'Destination',
    T2.Opotional AS 'SourceOpotional',
    T3.Opotional AS 'DestinationOpotional'
FROM @tbl2 T2
LEFT JOIN @tbl1 T1 ON T1.Prikey=T2.TankSourceID
LEFT JOIN @tbl3 T3 ON T2.TankSourceID=T3.TankDestinationID
LEFT JOIN @tbl1 T1_2 ON T3.TankDestinationID=T1_2.Prikey