/*----------------------------------------------
  Beispiele zum Abschnitt Thetajoin
  ----------------------------------------------
  Autor: Vinzenz Mai
  ----------------------------------------------
  Erstellungsdatum: 2005-11-24
----------------------------------------------*/

/*----------------------------------------------
  Beispiel 1 - SELFJOIN der Tab. Kreditkarten
----------------------------------------------*/  
SELECT
  KK1.KndNr,
  KK1.Firma,
  KK2.KndNr,
  KK2.Firma
FROM Kreditkarten AS KK1
INNER JOIN Kreditkarten AS KK2
ON KK1.KndNr = KK2.KndNr

/*----------------------------------------------
  Beispiel 2 - SELFJOIN der Tab. Kreditkarten
               Einschränkung des Ergebnisses
               durch die WHERE-Klausel
----------------------------------------------*/  
SELECT
  KK1.KndNr,
  KK1.Firma,
  KK2.KndNr,
  KK2.Firma
FROM Kreditkarten AS KK1
INNER JOIN Kreditkarten AS KK2
ON KK1.KndNr = KK2.KndNr
WHERE KK1.Firma = 'Mastercard' AND KK2.Firma = 'American Express'