From: | Grzegorz Szpetkowski <gszpetkowski(at)gmail(dot)com> |
---|---|
To: | pgsql-docs(at)postgresql(dot)org |
Subject: | Re: 7.2. Table Expressions suggestion about NATURAL JOIN |
Date: | 2011-05-18 01:52:35 |
Message-ID: | BANLkTine881x0Jb8NeO38baToKhZ3HHybA@mail.gmail.com |
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Lists: | pgsql-docs |
2011/5/18 Grzegorz Szpetkowski <gszpetkowski(at)gmail(dot)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
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