http://www.postgresql.org/docs/9.0/static/queries-table-expressions.htmlhttp://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
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