Thread: Postgresql function which compares values from both tables
<div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt">hi ,<br/>how to write a function which should read data from 2 tables having same number of columns and should show the commonvalues from those tables.<br />thanks<br /></div>
You would need to install the “HSTORE” extension to convert the record into a key->value pair then perform the comparison on that.
Dave
From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org] On Behalf Of Rehan Saleem
Sent: Monday, March 19, 2012 3:40 PM
To: pgsql-sql@postgresql.org
Subject: [SQL] Postgresql function which compares values from both tables
hi ,
how to write a function which should read data from 2 tables having same number of columns and should show the common values from those tables.
thanks
On 19/03/12 20:04, David Johnston wrote: > You would need to install the “HSTORE” extension to convert the record > into a key->value pair then perform the comparison on that. No, you can do this just fine with a simple join. BEGIN; CREATE TABLE ta (id int PRIMARY KEY, d date, t text); CREATE TABLE tb (id int PRIMARY KEY, d date, t text); INSERT INTO ta SELECT 100+n, '2001-01-01'::date + n, 'entry ' || n FROM generate_series(1,19) n; INSERT INTO tb SELECT 200+n, '2001-01-01'::date + n, 'entry ' || n FROM generate_series(1,19) n; SELECT ta.id AS id_a, tb.id AS id_b, ta.d, ta.t FROM ta JOIN tb USING (d,t); ROLLBACK; If the fields were named differently you'd need something like: FROM ta JOIN tb ON (ta.d1, ta.t1) = (tb.d2, tb.t2) -- Richard Huxton Archonet Ltd
> -----Original Message----- > From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql- > owner@postgresql.org] On Behalf Of Richard Huxton > Sent: Monday, March 19, 2012 4:59 PM > To: David Johnston > Cc: 'Rehan Saleem'; pgsql-sql@postgresql.org > Subject: Re: [SQL] Postgresql function which compares values from both > tables > > On 19/03/12 20:04, David Johnston wrote: > > You would need to install the "HSTORE" extension to convert the record > > into a key->value pair then perform the comparison on that. > > No, you can do this just fine with a simple join. > > BEGIN; > > CREATE TABLE ta (id int PRIMARY KEY, d date, t text); CREATE TABLE tb (id int > PRIMARY KEY, d date, t text); > > INSERT INTO ta > SELECT 100+n, '2001-01-01'::date + n, 'entry ' || n FROM > generate_series(1,19) n; > > INSERT INTO tb > SELECT 200+n, '2001-01-01'::date + n, 'entry ' || n FROM > generate_series(1,19) n; > > SELECT ta.id AS id_a, tb.id AS id_b, ta.d, ta.t FROM ta JOIN tb USING (d,t); > > ROLLBACK; > > If the fields were named differently you'd need something like: > FROM ta JOIN tb ON (ta.d1, ta.t1) = (tb.d2, tb.t2) > I think I read into the question too much. If you want to find matching rows then ( ROW(alias_1.*) = ROW(alias_2.*) ) will work (and you do not even have to specify the columns explicitly). Read this for details. Note that if any of the columns can be NULL you need to be especially careful. http://www.postgresql.org/docs/9.0/interactive/functions-comparisons.html I was thinking that you wanted to know which specific columns matched even if the row as a whole did not. Dave J.
<font face="sans-serif" size="2">Hi,</font><br /><font face="sans-serif" size="2">> To: pgsql-sql@postgresql.org<br />> Subject: [SQL] Postgresql function which compares values from both tables</font><br /><font face="sans-serif" size="2">> </font><br /><font face="sans-serif" size="2">> hi ,<br /> > how to write a function which should readdata from 2 tables having <br /> > same number of columns and should show the common values from those tables.<br/> If you want to compare and ensure that the values are same for <b>all</b> columns, please have a look at INTERSECT</font><br/><a href="http://www.postgresql.org/docs/9.1/static/sql-select.html"><font face="sans-serif" size="2">http://www.postgresql.org/docs/9.1/static/sql-select.html</font></a><br/><font face="sans-serif" size="2">Regards,</font><br/><font face="sans-serif" size="2">Jayadevan<br /></font><br /><font face="sans-serif" size="2"><br/><br /><br /><br /> DISCLAIMER:</font><font size="3"> </font><font color="#a2a2a2" face="Tahoma" size="1"><br/><br /> "The information in this e-mail and any attachment is intended only for the person to whom it is addressedand may contain confidential and/or privileged material. If you have received this e-mail in error, kindly contactthe sender and destroy all copies of the original communication. IBS makes no warranty, express or implied, nor guaranteesthe accuracy, adequacy or completeness of the information contained in this email or any attachment and is notliable for any errors, defects, omissions, viruses or for resultant loss or damage, if any, direct or indirect."</font><fontsize="3"><br /></font><font size="1"><br /></font><font size="3"><br /></font><br /><br />