Re: SELECT documentation

On Sat, Aug 13, 2022 at 10:21:26PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > Hi, I agree we should show the more modern JOIN sytax. However, this is
> > just an example, so one example should be sufficient. I went with the
> > first one in the attached patch.
>
> You should not remove the CROSS JOIN mention at l. 604, first because
> the references to it just below would become odd, and second because
> then it's not explained anywhere on the page. Perhaps you could
> put back a definition of CROSS JOIN just below the entry for NATURAL,
> but you'll still have to do something with the references at l. 614,
> 628, 632.

Good point. I restrutured the docs to move CROSS JOIN to a separate
section like NATURAL and adjusted the text, patch attached.

> Also, doesn't "[ AS join_using_alias ]" apply to NATURAL and CROSS
> joins? You've left that out of the syntax summary.

Uh, I only see it for USING in gram.y:

/* JOIN qualification clauses
* Possibilities are:
* USING ( column list ) [ AS alias ]
* allows only unqualified column names,
* which must match between tables.
* ON expr allows more general qualifications.
*
* We return USING as a two-element List (the first item being a sub-List
* of the common column names, and the second either an Alias item or NULL).
* An ON-expr will not be a List, so it can be told apart that way.
*/

join_qual: USING '(' name_list ')' opt_alias_clause_for_join_using
{
$$ = (Node *) list_make2($3, $5);
}
| ON a_expr
{
$$ = $2;
}
;

...

/*
* The alias clause after JOIN ... USING only accepts the AS ColId spelling,
* per SQL standard. (The grammar could parse the other variants, but they
* don't seem to be useful, and it might lead to parser problems in the
* future.)
*/
opt_alias_clause_for_join_using:
AS ColId
{
$$ = makeNode(Alias);
$$->aliasname = $2;
/* the column name list will be inserted later */
}
| /*EMPTY*/ { $$ = NULL; }
;

which is only used in:

| table_ref join_type JOIN table_ref join_qual
| table_ref JOIN table_ref join_qual

I have updated my private build:

https://momjian.us/tmp/pgsql/sql-select.html

--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com

Indecision is a decision. Inaction is an action. Mark Batterson