Обсуждение: Bug about column references within subqueries used in selects

Hi, <br /><br />Shouldn't the final command below cause a 'column "b" does not exist error'?<br /><br />create table
update_test(a int, b int);<br />create table supdate_test(x int, y int);<br />insert into update_test values (20, 30);
<br/>insert into supdate_test values (40, 50);<br />select a, (select b from supdate_test) from update_test;<br /><br
/>        a  ?column?<br />---------- -------------------------<br />        20        30<br /><br />Is the problem
withthe code in colNameToVar or maybe we should add checks in transformSubLink? <br /><br clear="all" />Regards,<br
/>Nikhils<br/>-- <br />EnterpriseDB               <a href="http://www.enterprisedb.com">http://www.enterprisedb.com</a> 

On 4/12/07, NikhilS <nikkhils@gmail.com> wrote:
> Hi,
>
> Shouldn't the final command below cause a 'column "b" does not exist error'?
>
> create table update_test (a int, b int);
> create table supdate_test(x int, y int);
> insert into update_test values (20, 30);
> insert into supdate_test values (40, 50);
> select a, (select b from supdate_test) from update_test;
>
>          a  ?column?
> ---------- -------------------------
>         20        30
>
> Is the problem with the code in colNameToVar or maybe we should add checks
> in transformSubLink?

I don't think so...the columns of update_test are visible to the
scalar subquery...that way you can use fields from 'a' to filter the
subquery...
select a, (select y from supdate_test where x = a) from update_test;

merlin

>
>     I don't think so...the columns of update_test are visible to the
>     scalar subquery...that way you can use fields from 'a'
> to filter the
>     subquery...
>     select a, (select y from supdate_test where x = a) from
> update_test;
>
>
> Yes this is fine, but in "select columnname from tablename"
> using column references of the other involved table is what I
> am objecting to.
>

There's nothing here to object to, the system is acting correctly. Your
column name "b" is ambiguous, and the system takes the column "b" that
exists, rather than returning an error on a column that doesn't exist.
If you were explicit in your column name, you would get an error:

=# select a, (select supdate_test.b from supdate_test) from update_test;
ERROR:  No such attribute supdate_test.b

Regards,
Paul

NikhilS <nikkhils@gmail.com> writes:
> Yes this is fine, but in "select columnname from tablename" using column
> references of the other involved table is what I am objecting to.

You can object till you're blue in the face, but this behavior is not
changing because it's *required by spec*.  Outer references are a
standard and indeed essential part of SQL.
        regards, tom lane