Re: Why *no* ambig·uous complain in select part?

Emi Lu <emilu@encs.concordia.ca> writes:
> Just notice one small thing, and need your information about select

> select col1, col2
> from table1
> left join table2
> using (col1, col2)
> ;

> This query never complain about ambiguous columns of col1 and col2 in
> the select part.

That's because you used USING, which merges the similarly-named columns
into just one output column.  RTFM, or any SQL book.

            regards, tom lane