Re: No error when FROM is missing in subquery

>>> On Mon, Dec 18, 2006 at 11:48 PM, in message
<15735(dot)1166507302(at)sss(dot)pgh(dot)pa(dot)us>,
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> The reason there's no error thrown is that the reference to mov_id
in
> the sub- SELECT is a perfectly legal outer reference to the mov_id
column
> available from the upper SELECT. If the column truly did not exist
> anywhere in the tables used in the query, it would have thrown an
error.

It's easy to see how it resolves the column references; but the syntax
is still not compliant with the SQL standard. The FROM clause is
required. We could call it a PostgreSQL extension, but I'm curious if
anyone actually finds it useful. So far it just seems to provide an
opportunity for error.

-Kevin

*scalar_subquery
: subquery
;

*subquery
: LEFT_PAREN query_expression RIGHT_PAREN
;

*query_expression
: non_join_query_expression
| joined_table
;

*non_join_query_expression
: non_join_query_term
| query_expression TK_union [ TK_all ]
[ corresponding_spec ] query_term
| query_expression TK_except [ TK_all ]
[ corresponding_spec ] query_term
;

*non_join_query_term
: non_join_query_primary
| query_term TK_intersect [ TK_all ]
[ corresponding_spec ] query_primary
;

*non_join_query_primary
: simple_table
| LEFT_PAREN non_join_query_expression RIGHT_PAREN
;

*simple_table
: query_specification
| table_value_constructor
| explicit_table
;

*query_specification
: TK_select [ set_quantifier ] select_list table_expression
;

*select_list
: ASTERISK
| select_sublist [ { COMMA select_sublist }... ]
;

*select_sublist
: derived_column
| qualifier PERIOD ASTERISK
;

*derived_column
: value_expression [ as_clause ]
;

*as_clause
: [ TK_as ] column_name
;

*table_expression
: from_clause
[ where_clause ]
[ group_by_clause ]
[ having_clause ]
;

*from_clause
: TK_from table_reference
[ { COMMA table_reference }... ]
;