How to resolve ORA-00937: not a single-group group function when calculating percentage?

Question

I\'m trying to get a percentage of the itemid that are available in a certain area. Using my query, I get an error ORA-00937: not a single-group group function<

Answer 1

Just for the heck of it, a way of doing it without analytics.

Jeffrey's solution needed a DISTINCT because of the duplication of areas. The allitems table is actually an intersection table between currentitems and a putative areas table. In the following query this is represented by the inline view ai. There is another inline view tot which gives us the total number number of records in allitems. This count has to be included in the GROUP BY clause, as it is not an aggregating projector.

SQL> select ai.areas
  2         , (count(currentitems.itemid)/tot.cnt) * 100 as "%"
  3  from
  4      ( select count(*) as cnt from allitems ) tot
  5      , ( select distinct areas as areas from allitems ) ai
  6      , currentitems
  7      , allitems
  8  where allitems.areas = ai.areas
  9  and   allitems.itemid = currentitems.itemid(+)
 10  group by ai.areas, tot.cnt
 11  /

AREAS                         %
-------------------- ----------
east                         50
south                        25
west                          0

SQL>

I don't know whether this approach would perform better than Jeffrey's solution: it quite possibly will perform worse (the analytics query certainly has fewer consistent gets). It is interesting simply because it highlights the issues more clearly.