[GENERAL] what's wrong with this query

[Thomas T. Thai]

still trying to port this app from mysql to pgsql, but getting this error:

Database error: Invalid SQL: select
t_stories.heading,t_stories.rid,count(*) as cmts from t_stories,t_comments
where t_comments.toprid = t_stories.rid and t_stories.verified = 'y' group
by t_comments.toprid order by t_stories.hits desc limit 5
PostgreSQL Error: 1 (ERROR: Attribute t_stories.heading must be GROUPed or
used in an aggregate function )
Session halted.

what's wrong with that query?