TSQL Reference Table with redundant keys - sql-server

Question

I'm currently working on a stored procedure on SQL Server 2016. In my Database I have a table structure and need to add another table, which references to the same table as an existing one.
Thus, I have 2 times a 1:1 relation to the same table.
The occuring problem is, I reference the same keys from 2 different origin tables twice in the same target table.
Target table:
FK_Tables | Text
----------------
1 | Table One Text Id: 1
1 | Table Two Text Id: 1 // The error: Same FK_Tables 2 times
Table One:
ID | OtherField
---------
1 | 42
Table Two:
ID | CoolField
---------
1 | 22
Table One and Table Two are currently referencing to the table Reference Table.
Do you know how I can solve this problem, of the same ID twice?
Thanks!!

Answer 1

You need to add a column for each table you're referencing, otherwise you wouldn't know where the ID is coming from if they were all inserted into the same field. Something like this:
/*
CREATE TEST TABLES
*/
DROP TABLE IF EXISTS tbOne;
CREATE TABLE tbOne ( ID INT IDENTITY(1,1) NOT NULL PRIMARY KEY
, TXT VARCHAR(10)
);
DROP TABLE IF EXISTS tbTwo;
CREATE TABLE tbTwo ( ID INT IDENTITY(1,1) NOT NULL PRIMARY KEY
, TXT VARCHAR(10)
);
DROP TABLE IF EXISTS Target;
CREATE TABLE Target ( ID INT IDENTITY(1,1) NOT NULL PRIMARY KEY
, FKTB1 INT
, FKTB2 INT
, TXT VARCHAR(100)
);
-- 1st FK tbOne
ALTER TABLE Target ADD CONSTRAINT FK_One FOREIGN KEY (FKTB1) REFERENCES tbOne (ID);
--2nd FK tbTwo
ALTER TABLE Target ADD CONSTRAINT FK_Two FOREIGN KEY (FKTB2) REFERENCES tbTwo (ID);
-- Populate test tables
INSERT INTO tbOne (TXT)
SELECT TOP 100 LEFT(text, 10)
FROM SYS.messages
INSERT INTO tbTwo (TXT)
SELECT TOP 100 LEFT(text, 10)
FROM SYS.messages
INSERT INTO [Target] (FKTB1, FKTB2, TXT)
SELECT 1, 1, 'Test - constraint'
-- Check result set
SELECT *
FROM tbTwo
SELECT *
FROM tbOne
SELECT *
FROM [Target] T
INNER JOIN tbOne TB1
ON T.FKTB1 = TB1.ID
INNER JOIN tbTwo TB2
ON T.FKTB2 = TB2.ID