Re: Question About UNION

David Wilson wrote:
> On Thu, Oct 9, 2008 at 1:48 PM, Bill Thoen <bthoen@gisnet.com> wrote:
>
>> No, this won't work. Here's an example of my tables:
>> Table1
>> 1, 12, A
>> 2, 16, B
>> 8, 6, A
>> 19, 9, C
>>
>> Table2
>> 1, 13, D
>> 2, 16, B
>> 8, 6, B
>> 12, 5, A
>>
>
> select * from table1
> union
> select table2.* from table2 left join table1 on table2.a=table1.a and
> table2.b=table1.b where table2.a is null;
>
> (Written in gmail, but you should get the basic idea.)
>
Thanks, but that didn't work. That selected only the records from
table1. However, this did work:
CREATE TABLE table3 AS
   SELECT * FROM table1;

CREATE UNIQUE INDEX table3_pk ON table3  (a, b);

INSERT INTO table3 SELECT * FROM table2
   WHERE NOT EXISTS (SELECT a, b FROM table1 t1
      WHERE table2.a=t1.a AND table2.b=t1.b);