On 15 July 2010 00:52, Richard Yen <richyen@xxxxxxxxxxxxxx> wrote: > Hi everyone, > > Looks like I'm encountering some quirks with coalesce()... > >> postgres=# select coalesce(null,0); >> coalesce >> ---------- >> 0 >> (1 row) >> >> postgres=# SELECT COALESCE(ROUND(EXTRACT(epoch FROM now()-query_start)),0) FROM pg_stat_activity WHERE current_query = '<IDLE> in transaction'; >> coalesce >> ---------- >> (0 rows) >> >> postgres=# select version(); >> version >> ------------------------------------------------------------------------------------------------------------------- >> PostgreSQL 8.4.2 on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-44), 64-bit >> (1 row) > > Any ideas? > --Richard > -- I don't see what you mean. The query can't return any rows because none match the criterion specified. If you'd normally get 0 rows if using SELECT *, then adding in coalesce isn't going to force a result as there's nothing to select against. postgres=# SELECT COALESCE(NULL,0) FROM pg_stat_activity WHERE current_query = '<IDLE> in transaction'; coalesce ---------- (0 rows) postgres=# select coalesce(null,0) from pg_database where 1 = 2; coalesce ---------- (0 rows) Thom -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
