Re: Group by bug?

[wd <wd@xxxxxxxxx>]

Sorry, forget to say,

 PostgreSQL 9.2.2 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.4.6 20110731 (Red Hat 4.4.6-3), 64-bit

 psql (9.2.2)

On Fri, Dec 28, 2012 at 3:24 PM, wd <wd@xxxxxxxxx> wrote:

hi,

wd_test=# \d t1
                         Table "public.t1"
 Column |  Type   |                    Modifiers                   
--------+---------+-------------------------------------------------
 id     | integer | not null default nextval('t1_id_seq'::regclass)
 tag    | text    |

wd_test=# select * from t1;
 id | tag
----+-----
  1 | a
  2 | a
  3 | b
  4 | c
  5 | b
(5 rows)

---- this sql will not group by the case result.

wd_test=# select case t1.tag when 'a' then '1' else '0' end as tag, count(*) from t1 group by tag;
 tag | count
-----+-------
 0   |     1
 0   |     2
 1   |     2
(3 rows)

---- this sql will group by the case result.
wd_test=# select case t1.tag when 'a' then '1' else '0' end as ttag, count(*) from t1 group by ttag;
 ttag | count
------+-------
 0    |     3
 1    |     2
(2 rows)