title: Sql Subselect ORA-00918
body: <p>This is my Sql: </p>
  
  <pre><code>SELECT 
      t.RUFNAME,
      count(v_anschrift.rufname) as Anrufe
  FROM v_termin,
  (
      SELECT 
      RUFNAME
      FROM
      V_Anschrift
      WHERE V_ANSCHRIFT.SPERRKZ = 0
      AND V_ANSCHRIFT.OEM != 0 
  ) t
  JOIN v_anschrift ON (t.Rufname = v_anschrift.RUFNAME)
  LEFT JOIN v_termin ON (v_termin.anschriftid = v_anschrift.anschriftid)
  WHERE v_termin.TERMINART = 20
  GROUP BY t.RUFNAME;
  </code></pre>
  
  <p>And i get this error message:</p>
  
  <blockquote>
    <p>ORA-00918: Spalte nicht eindeutig definiert
    00918. 00000 -  "column ambiguously defined"
    *Cause:<br>
    *Action:
    Fehler in Zeile: 15 Spalte: 7</p>
  </blockquote>
  
  <p>where is my mistake?</p>