Re: Learning about WITH RECURSIVE

On Wed, Nov 4, 2009 at 2:11 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Richard Broersma <richard(dot)broersma(at)gmail(dot)com> writes:
>> Can anyone one explain why a "WITH RECURSIVE" query has the same
>> results regardless whether UNION or UNION ALL is specified?
>
> Well, if the rows are all different anyway, UNION isn't going to
> eliminate any ...

Actually I'm still confused. I must me missing something. When I
manually following the directions of:
http://www.postgresql.org/docs/8.4/interactive/queries-with.html

I get the following when I try:

WITH RECURSIVE t(n) AS (
VALUES (1)
UNION ALL
SELECT n+1 FROM t WHERE n < 100
)
SELECT sum(n) FROM t;

(1) --initial non-recursive working table

(1) UA (2) = (1,2) --new(1) working table

(1,2) UA (2,3) = (1,2,2,3) --new(2) working table

(1,2,2,3) UA (2,3,3,4) = (1,2,2,2,3,3,3,4) --new(3) working table

--
Regards,
Richard Broersma Jr.

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