Ich denke mal, dass er ein Feld in die GroupBy Klausel aufnehmen möchte, welches nicht im Select steht => dann hakt's natürlich
Edit: Oracle meint dazu übrigens folgendes:
Zitat:
ORA-00979 not a GROUP BY expression
Cause: The GROUP BY clause does not contain all the expressions in the SELECT clause. SELECT expressions that are not included in a group function, such as AVG, COUNT, MAX, MIN, SUM, STDDEV, or VARIANCE, must be listed in the GROUP BY clause.
Action: Include in the GROUP BY clause all SELECT expressions that are not group function arguments.