Re: Is this a bug? Deleting a column deletes the constraint.

dev(at)freedomcircle(dot)net (Joe) writes:
> On Thu, 2006-10-12 at 01:25 -0400, Tom Lane wrote:
>> It does seem like this is wrong, in view of SQL92's statement about
>> ALTER TABLE DROP COLUMN:
>>
>> 4) If RESTRICT is specified, then C shall not be referenced in
>> the <query expression> of any view descriptor or in the <search
>> condition> of any constraint descriptor other than a table con-
>> straint descriptor that contains references to no other column
>> and that is included in the table descriptor of T.
>>
>> IOW we should only allow unique constraints to be auto-dropped if
>> they reference just the one single column. Ick.
>
> I didn't realize before that you can also drop all columns, leaving a
> table without *any* columns. Is that a SQL92 "feature"?

You can create a table without any columns.

tutorial=# create table empty_table ();
CREATE TABLE
tutorial=# \d empty_table
Table "public.empty_table"
Column | Type | Modifiers
--------+------+-----------

tutorial=# select * from empty_table ;

--
(0 rows)

A table without columns is of pretty limited usefulness, until you add
some columns, but having a form of "zero" seems not insensible...
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