SQL: 2 Foreign Keys referencing one Primary Key - sql

Question

I have a database diagram and need to create a Database with different tables.
This is my code:
use FirmaLieferungen;
drop table liefert;
drop table rabatt;
drop table artikel;
drop table firma;
SET DATEFORMAT dmy;
create table firma (
fnr integer primary key,
name char(10),
jahrgruendung integer, -- Gründungsjahr
land char(3)
);
insert into firma values (101,'Schwer' ,1890,'A' );
insert into firma values (102,'Schmal' ,1901,'CH' );
insert into firma values (103,'Tief' ,1945,'I' );
insert into firma values (104,'Breit' ,1950,'A' );
insert into firma values (105,'Leicht' ,1945,'F' );
insert into firma values (106,'Hoch' ,1920,'CH' );
insert into firma values (107,'Hell' ,1900,'A' );
create table artikel (
fnr integer,
lfdnr integer,
bezeichnung char(10),
preis decimal(6,2),
einheit char(3),
land char(3),
primary key(fnr, lfdnr),
foreign key(fnr) references firma
);
insert into artikel values (101,1,'Schaufel' ,12.30,'Stk','A' );
insert into artikel values (101,2,'Hacke' ,15.20,'Stk','F' );
insert into artikel values (102,1,'Spaten' ,13.00,'Stk','A' );
insert into artikel values (103,1,'Schere' , 8.00,'Stk','A' );
insert into artikel values (103,2,'Messer' ,10.60,'Stk','F' );
insert into artikel values (103,3,'Schnur' , 1.10,'m' ,'D' );
insert into artikel values (105,1,'Schnur' , 0.40,'m' ,'D' );
insert into artikel values (106,1,'Hacke' ,20.70,'Stk','CH' );
insert into artikel values (106,2,'Draht' , 0.60,'m' ,'CH' );
create table liefert (
fnrvon integer,
fnran integer,
fnr integer,
lfdnr integer,
datum date,
menge decimal(8,2)
primary key(fnrvon, fnran, fnr, lfdnr, datum),
foreign key(fnr, lfdnr) references artikel,
foreign key(fnr) references firma
);
insert into liefert values (101,102,101,1,'01.02.1999', 3.00);
insert into liefert values (101,102,101,1,'02.01.2000', 2.00);
insert into liefert values (101,104,101,2,'13.02.2000', 11.00);
insert into liefert values (101,104,101,1,'24.11.1999', 19.00);
insert into liefert values (101,105,103,3,'31.03.2001', 1553.00);
insert into liefert values (102,101,102,1,'21.04.1999', 28.00);
insert into liefert values (102,101,101,1,'11.12.1999', 1.00);
insert into liefert values (102,104,101,1,'04.07.2000', 63.00);
insert into liefert values (103,101,103,3,'21.04.1999', 3.25);
insert into liefert values (103,104,101,1,'08.02.1998', 17.00);
insert into liefert values (104,102,105,1,'19.11.2001', 132.50);
insert into liefert values (104,106,101,1,'04.07.2000', 22.00);
insert into liefert values (106,102,101,1,'07.08.2002', 81.00);
insert into liefert values (106,102,106,2,'01.06.2002', 21.30);
insert into liefert values (106,104,101,1,'26.09.2001', 2.00);
create table rabatt (
fnrvon integer,
fnran integer,
prozent decimal (5,2),
primary key (fnrvon, fnran),
foreign key (fnrvon, fnran) references firma
);
insert into rabatt values (101,102, 5.25);
insert into rabatt values (102,101, 5.50);
insert into rabatt values (101,103,15.75);
insert into rabatt values (103,102, 7.50);
insert into rabatt values (102,103,10.50);
insert into rabatt values (105,106, 5.25);
insert into rabatt values (104,101, 7.50);
select * from rabatt;
select * from firma;
select * from liefert;
select * from artikel;
But there's an error in the 'rabatt' creation, it says that the last command is invalid.
foreign key (fnrvon, fnran) references firma
This is somehow wrong, but I don't know why... Is the diagram wrong? There are also two keys going from 'liefert' to 'firma' how do I do this? Please help me!
Thanks! (I'm using Microsoft SQL Server 2008)

Answer 1

When you reference another table, you should specify which column(s) you are referencing.
So, for example:
create table liefert (
fnrvon integer,
fnran integer,
fnr integer,
lfdnr integer,
datum date,
menge decimal(8,2)
primary key(fnrvon, fnran, fnr, lfdnr, datum),
foreign key(fnr, lfdnr) references artikel (fnr, lfdnr),
foreign key(fnr) references firma (fnr)
);

Answer 2

Mureinik is right, just answered 1 sec before me.
For the sake of the question I crated a Fiddle Improve it for further questions
http://sqlfiddle.com/#!6/6a1b7

Answer 3

Your firma table doesn't have columns named fnrvon or fnran so
foreign key (fnrvon, fnran) references firma
fails to figure out what is referenced.
You need to be explicit. Also, If the two columns are both referencing the same foreign key, then it needs to be two separate statements
foreign key (fnran) references firma (fnr)
foreign key (fnrvon) references firma (fnr)