On Fri, 17 Jan 2003, Bruno Wolff III wrote:
> On Fri, Jan 17, 2003 at 08:57:14 -0500,
> Andrew Perrin <clists@perrin.socsci.unc.edu> wrote:
> >
> > that way you avoid duplicates across tables.
>
> The union operator already removes duplicates.
Right, which means everyone's UNION queries have too many DISTINCTs
in them:
SELECT email from table1
UNION
SELECT email from table2 ;
should do it.
Here's proof: note the duplicate 'foo' and 'bar':
test=# select * from table1;
email
-----------------
foo@example.com
bar@example.com
bar@example.com
(3 rows)
test=# select * from table2;
email
------------------
quux@example.com
foo@example.com
(2 rows)
test=# select email
test=# select email from table1 union select email from table2;
email
------------------
bar@example.com
foo@example.com
quux@example.com
(3 rows)
Ross
--
Ross Reedstrom, Ph.D. reedstrm@rice.edu
Research Scientist phone: 713-348-6166
The Connexions Project http://cnx./rice.edu fax: 713-348-6182
Rice University MS-39
Houston, TX 77005
