activerecord issues with rails 3 postgresql

[amruby]

i have one query 

@recommendations = Recommendation.select('cnames.name,max(recommendations.count)').

                  where('recommendations.skill= ?',@key).

                  order('recommendations.company_id ASC').

                  group('recommendations.company_id').

                  joins('JOIN recommendations ON cnames.id = recommendations.company_id')

when i run this query i got this error

PG::Error: ERROR:  table name "recommendations" specified more than once

Why it shows like that?

[Matt Jones]

Since you're querying on the Recommendation model, there's already a 'FROM recommendations' clause in the generated query. You probably meant 'cnames' in that joins call.

You'll also run into Postgres's rules about using ungrouped values in the SELECT part; the above query won't be legal even with a correct join.

--Matt Jones