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7.2. Table Expressions suggestion about NATURAL JOIN 4+ messages / 2 participants [nested] [flat]
* 7.2. Table Expressions suggestion about NATURAL JOIN @ 2011-05-18 01:47 Grzegorz Szpetkowski <[email protected]> 2011-05-18 01:52 ` Re: 7.2. Table Expressions suggestion about NATURAL JOIN Grzegorz Szpetkowski <[email protected]> 2011-06-13 17:00 ` Re: 7.2. Table Expressions suggestion about NATURAL JOIN Robert Haas <[email protected]> 0 siblings, 2 replies; 4+ messages in thread From: Grzegorz Szpetkowski @ 2011-05-18 01:47 UTC (permalink / raw) To: pgsql-docs 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 ^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: 7.2. Table Expressions suggestion about NATURAL JOIN 2011-05-18 01:47 7.2. Table Expressions suggestion about NATURAL JOIN Grzegorz Szpetkowski <[email protected]> @ 2011-05-18 01:52 ` Grzegorz Szpetkowski <[email protected]> 1 sibling, 0 replies; 4+ messages in thread From: Grzegorz Szpetkowski @ 2011-05-18 01:52 UTC (permalink / raw) To: pgsql-docs 2011/5/18 Grzegorz Szpetkowski <[email protected]>: > 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 ^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: 7.2. Table Expressions suggestion about NATURAL JOIN 2011-05-18 01:47 7.2. Table Expressions suggestion about NATURAL JOIN Grzegorz Szpetkowski <[email protected]> @ 2011-06-13 17:00 ` Robert Haas <[email protected]> 1 sibling, 0 replies; 4+ messages in thread From: Robert Haas @ 2011-06-13 17:00 UTC (permalink / raw) To: Grzegorz Szpetkowski <[email protected]>; +Cc: pgsql-docs On Tue, May 17, 2011 at 9:47 PM, Grzegorz Szpetkowski <[email protected]> wrote: > 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. Done, with different wording. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company ^ permalink raw reply [nested|flat] 4+ messages in thread
* 7.2. Table Expressions suggestion about NATURAL JOIN @ 2011-05-18 01:47 Grzegorz Szpetkowski <[email protected]> 0 siblings, 0 replies; 4+ messages in thread From: Grzegorz Szpetkowski @ 2011-05-18 01:47 UTC (permalink / raw) To: pgsql-docs 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 -- Sent via pgsql-docs mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-docs ^ permalink raw reply [nested|flat] 4+ messages in thread
end of thread, other threads:[~2011-06-13 17:00 UTC | newest] Thread overview: 4+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2011-05-18 01:47 7.2. Table Expressions suggestion about NATURAL JOIN Grzegorz Szpetkowski <[email protected]> 2011-05-18 01:52 ` Grzegorz Szpetkowski <[email protected]> 2011-06-13 17:00 ` Robert Haas <[email protected]> 2011-05-18 01:47 7.2. Table Expressions suggestion about NATURAL JOIN Grzegorz Szpetkowski <[email protected]>
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