1
a)
```SQL 
create or REPLACE FUNCTION summeWarenkorb(kID in number) RETURN NUMBER

IS

output number DEFAULT 0;

BEGIN

    SELECT SUM(PREIS*anzahl) into output

    From WARENKORB

    join ARTIKEL on WARENKORB.ARTIKELNUMMER=ARTIKEL.ARTIKELNUMMER

    WHERE KUNDENNUMMER=kID;

    RETURN output;

END;
```
```SQL 
SELECT Kundennummer, summeWarenkorb(Kundennummer) FROM Kunde WHERE summeWarenkorb(Kundennummer) IS NOT NULL;
```
b) 
```SQL 
CREATE OR REPLACE FUNCTION Lagerbestandabfrage (artnr IN NUMBER) RETURN number

IS

output number default 0;

BEGIN

    SELECT sum(LAGERBESTAND) into output

    FROM LAGER

    WHERE ANUMMER=artnr;

    RETURN output;

END;
```
```SQL 
SELECT DISTINCT ANummer, Lagerbestandabfrage(ANummer) FROM lager;
```

2
a)