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@wdicc.com> 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)
