Problem trying to use a group by clause

Question

hey good day,
i'm trying to use a group by clause in my application, but I'm getting the following error.
Error:-  Query cannot be parsed, please check the syntax of your query. (ORA-00979: not a GROUP BY expression)
select      "INSTRUCTOR"."EMPNUM",
      "INSTRUCTOR"."FIRSTNAME",
      "INSTRUCTOR"."LASTNAME",
      "QUALN"."SPECIALIZE_FIELD" as "SPECIALIZE_FIELD",
         "INSTRUCTOR"."USERNAME"
from      "QUALN" "QUALN",
      "INSTRUCTOR" "INSTRUCTOR"
where   "INSTRUCTOR"."EMPNUM"="QUALN"."EMPNUM"
group by "INSTRUCTOR"."EMPNUM", "INSTRUCTOR"."FIRSTNAME", "INSTRUCTOR"."LASTNAME"Thanks in advance,
Richie

Answer 1

Richie wrote:
hey thanks for your reply,
i have tried what you have suggested, but now i got another error
Error :- The report query needs a unique key to identify each row. The supplied key cannot be used for this query. Please edit the report attributes to define a unique key column. ORA-01446: cannot select ROWID from, or sample, a ...
This error message is not from oracle, btu from your reporting tool. it might be MS Access or whatever other tool that you use. Some of these tools want a unique value to identify the current row. The logic applied depends on the relationship of your tables. however in your case you could do it without the group by condition. THen the rowid can still be applied to your query.
Example
note the usage of alias names to simplified the select
select      i.EMPNUM ,
      i.FIRSTNAME ,
      i.LASTNAME ,
         i.USERNAME
from      INSTRUCTOR i
where   i.EMPNUM in (select q.EMPNUM from QUALN q);