Re: SQL state: 42P01

"David Monarchi" <david.e.monarchi@gmail.com> writes:
> When I execute the following query,
> select A.domain_name_dom, A.word_wdl, A.count_ofi, A.total_quality_ofi,
> A.avg_quality_ofi
>   from zzz_brand2domain_step2_bs2 as A join
>         (select B.domain_ofi, B.word_ofi, B.count_ofi, B.total_quality_ofi,
> B.avg_quality_ofi
>            from offpagedomainwordintersection_ofi as B
>              where B.domain_ofi != A.domain_name_dom
>              order by B.total_quality_ofi desc
>              limit 1) as C
>          on A.word_wdl = B.word_ofi;

> I receive this error message
> ERROR:  invalid reference to FROM-clause entry for table "a"
> LINE 5:              where B.domain_ofi != A.domain_name_dom
>                                            ^
> HINT:  There is an entry for table "a", but it cannot be referenced from
> this part of the query.

> I don't understand why I can't reference the respective tables in the
> queries.

Because a JOIN happens between two *independent* tables.  The above
isn't well-defined.

            regards, tom lane