Re: Synopsis of SELECT statement: UNION, INTERSECTION, EXCEPT

As a first step we could do something like:

​basic_select_statement is:
​

> SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]
> [ * | expression [ [ AS ] output_name ] [, ...] ]
> [ FROM from_item [, ...] ]
> [ WHERE condition ]
> [ GROUP BY grouping_element [, ...] ]
> [ HAVING condition [, ...] ]
> [ WINDOW window_name AS ( window_definition ) [, ...] ]
>

​full_select_statement is basic_select_statement with the following
possible additional clauses tacked onto the end:

[ ORDER BY expression [ ASC | DESC | USING operator ] [ NULLS { FIRST |
> LAST } ] [, ...] ]
> [ LIMIT { count | ALL } ]
> [ OFFSET start [ ROW | ROWS ] ]
> [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ]
> [ FOR { UPDATE | NO KEY UPDATE | SHARE | KEY SHARE } [ OF table_name
> [, ...] ] [ NOWAIT | SKIP LOCKED ] [...] ]
>
> and that's still not right because ORDER BY et al can't be attached to a
> select_stmt that's the argument of a set operation, so really we'd need
> a couple of levels of nonterminals before we get down to the basic
> "SELECT expression FROM ..." part. Nor has the use of parentheses been
> mentioned yet.
>

​Then we can define the set clauses in terms of basic_select_stmt and
parentheses-surrounded full_select_stmt. The result of the set clause is
itself a type of basic_select_statement which can be made full by adding
one or more of the additional clauses, including ORDER BY.

David J.