Thread: Number of rows in a table
I haven’t been able to figure out how to determine the number of populated rows in a table – such as “select max(rownum)” in Oracle.
Thanks!
2003-08-25 ragyogó napján Louise Cofield ezt üzente: > I haven't been able to figure out how to determine the number of > populated rows in a table - such as "select max(rownum)" in Oracle. select count(*) from usw.; ? -- Tomka Gergely "S most - vajon barbárok nélkül mi lesz velünk? Ők mégiscsak megoldás voltak valahogy..."
Count()?
-----Original Message-----
From: pgsql-novice-owner@postgresql.org [mailto:pgsql-novice-owner@postgresql.org]On Behalf Of Louise Cofield
Sent: Monday, August 25, 2003 12:06 PM
To: pgsql-novice@postgresql.org
Subject: [NOVICE] Number of rows in a tableI haven’t been able to figure out how to determine the number of populated rows in a table – such as “select max(rownum)” in Oracle.
Thanks!
From: "Louise Cofield" <lcofield@box-works.com> To: <pgsql-novice@postgresql.org> Subject: [NOVICE] Number of rows in a table Date sent: Mon, 25 Aug 2003 10:06:28 -0600 SELECT count(ColumnName) FROM TableName; should do the trick Paul Butler > I haven't been able to figure out how to determine the number of > populated rows in a table - such as "select max(rownum)" in Oracle. > > > > Thanks! > > > > > > > >
Am Mo, 2003-08-25 um 18.14 schrieb Tomka Gergely: > 2003-08-25 ragyogó napján Louise Cofield ezt üzente: > > > I haven't been able to figure out how to determine the number of > > populated rows in a table - such as "select max(rownum)" in Oracle. > > select count(*) from usw.; ? Keep i mind Louise, that this is an aggregate function, i.e. all other columns you want to get in the same query must be GROUPed or used in an aggregate function, too. bye -- e-Trolley Sayegh & John, Nabil Sayegh Tel.: 0700 etrolley /// 0700 38765539 Fax.: +49 69 8299381-8 PGP : http://www.e-trolley.de
On Mon, 2003-08-25 at 11:08, paul butler wrote: > From: "Louise Cofield" <lcofield@box-works.com> > To: <pgsql-novice@postgresql.org> > Subject: [NOVICE] Number of rows in a table > Date sent: Mon, 25 Aug 2003 10:06:28 -0600 > > SELECT count(ColumnName) FROM TableName; > should do the trick Well yes, but in most other databases, there is a system table that stores the approximate number of records in each table, and querying that system table is a *lot* faster than sequentially reading a 100M row table. > > I haven't been able to figure out how to determine the number of > > populated rows in a table - such as "select max(rownum)" in Oracle. -- ----------------------------------------------------------------- Ron Johnson, Jr. ron.l.johnson@cox.net Jefferson, LA USA PETA - People Eating Tasty Animals
Ron Johnson <ron.l.johnson@cox.net> writes:
> Well yes, but in most other databases, there is a system table that
> stores the approximate number of records in each table, and querying
> that system table is a *lot* faster than sequentially reading a 100M
> row table.
If an approximate number is good enough, see pg_class.reltuples.
regards, tom lane
ron.l.johnson@cox.net (Ron Johnson) writes: > Well yes, but in most other databases, there is a system table that > stores the approximate number of records in each table, and querying > that system table is a *lot* faster than sequentially reading a 100M > row table. That relation would be pg_class, the domain is called "reltuples." It is only about as accurate as the last vacuum and/or analyze has made it, so if you don't fairly regularly vacuum tables, the approximation may not be very good. (Which is an argument in favor of vacuuming fairly often...) -- select 'cbbrowne' || '@' || 'libertyrms.info'; <http://dev6.int.libertyrms.com/> Christopher Browne (416) 646 3304 x124 (land)