I am getting ORA-00979 with the following query:
SELECT cr.review_sk, cr.cs_sk, cr.full_name, tolist(to_char(cf.fact_date, \'mm/dd/yyyy\')) \"appt\", cs.cs_i
In addition to the other answers, this error can result if there's an inconsistency in an order by clause. For instance:
select substr(year_month, 1, 4) ,count(*) as tot from schema.tbl group by substr(year_month, 1, 4) order by year_month