2011/5/18 Grzegorz Szpetkowski <gszpetkowski@gmail.com>:
> http://www.postgresql.org/docs/9.0/static/queries-table-expressions.html
> http://www.postgresql.org/docs/9.0/static/sql-select.html
>
> Respectively:
>
> "Finally, NATURAL is a shorthand form of USING: it forms a USING list
> consisting of all column names that appear in both input tables. As
> with USING, these columns appear only once in the output table."
>
> and
>
> "NATURAL is shorthand for a USING list that mentions all columns in
> the two tables that have the same names."
>
> To make that comprehensive you can add something like: "Note that if
> there is no any "shared" column between tables, then NATURAL JOIN acts
> like ON TRUE (that is, tables are cross-joined)", because it's not
> obvious.
>
> thanks & regards,
> greg szpetkowski
>
My mistake "NATURAL JOIN", better is to just write "NATURAL".
thanks & regards,
greg szpetkowski