I have built a new 1.54 db, importing data from many tables.
I want to find records that have a duplicate string field.
I have tried the following, but it returns an error:

select noteid, folderid, subject
from dbnotes
group by subject
having count(*) > 1

Noteid and folderid are primary and secondary keys.

I need to find any duplicate subject fields and show their folderid.
The above script returns the following error:

ISC ERROR CODE:335544569

ISC ERROR MESSAGE:
Dynamic SQL Error
SQL error code = -104
Invalid expression in the select list (not contained in either an
aggregate function or the GROUP BY clause)