Frequently Asked Questions (FAQ) for PostgreSQL
- Last updated: Wed Feb 2 12:44:03 EST 2005
+ Last updated: Thu Feb 24 19:33:07 EST 2005
Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
4.8) How do I perform regular expression searches and case-insensitive
regular expression searches? How do I use an index for
case-insensitive searches?
- 4.9) In a query, how do I detect if a field is NULL?
+ 4.9) In a query, how do I detect if a field is NULL? How can I sort on
+ whether a field is NULL or not?
4.10) What is the difference between the various character types?
4.11.1) How do I create a serial/auto-incrementing field?
4.11.2) How do I get the value of a SERIAL insert?
4.17) How do I perform an outer join?
4.18) How do I perform queries using multiple databases?
4.19) How do I return multiple rows or columns from a function?
- 4.20) Why can't I reliably create/drop temporary tables in PL/PgSQL
- functions?
+ 4.20) Why do I get "missing oid" errors when accessing temporary
+ tables in PL/PgSQL functions?
4.21) What encryption options are available?
Extending PostgreSQL
PostgreSQL Data Base Management System
Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
- Portions Copyright (c) 1994-6 Regents of the University of California
+ Portions Copyright (c) 1994-1996 Regents of the University of
+ California
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose, without fee, and without a written
1.4) Where can I get PostgreSQL?
The primary anonymous ftp site for PostgreSQL is
- ftp://ftp.PostgreSQL.org/pub. For mirror sites, see our main web site.
+ ftp://ftp.PostgreSQL.org/pub/. For mirror sites, see our main web
+ site.
1.5) Where can I get support?
EFNet.
A list of commercial support companies is available at
- http://techdocs.postg resql.org/companies.php.
+ http://techdocs.postgresql.org/companies.php.
1.6) How do I submit a bug report?
Visit the PostgreSQL bug form at
http://www.postgresql.org/support/submitbug.
- Also check out our ftp site ftp://ftp.PostgreSQL.org/pub to see if
+ Also check out our ftp site ftp://ftp.PostgreSQL.org/pub/ to see if
there is a more recent PostgreSQL version.
1.7) What is the latest release?
also browse the manuals online at http://www.PostgreSQL.org/docs.
There are two PostgreSQL books available online at
- http://www.PostgreSQL.org/docs/awbook.html and
+ http://www.postgresql.org/docs/books/awbook.html and
http://www.commandprompt.com/ppbook/. There is a list of PostgreSQL
books available for purchase at
http://techdocs.PostgreSQL.org/techdocs/bookreviews.php. There is also
1.10) How can I learn SQL?
- The PostgreSQL book at http://www.PostgreSQL.org/docs/awbook.html
- teaches SQL. There is another PostgreSQL book at
- http://www.commandprompt.com/ppbook. There is a nice tutorial at
+ The PostgreSQL book at
+ http://www.postgresql.org/docs/books/awbook.html teaches SQL. There is
+ another PostgreSQL book at http://www.commandprompt.com/ppbook. There
+ is a nice tutorial at
http://www.intermedia.net/support/sql/sqltut.shtm, at
http://ourworld.compuserve.com/homepages/graeme_birchall/HTM_COOK.HTM,
and at http://sqlcourse.com.
For Web integration, PHP (http://www.php.net) is an excellent
interface.
- For complex cases, many use the Perl and CGI.pm or mod_perl.
+ For complex cases, many use the Perl DBD::Pg with CGI.pm or mod_perl.
2.3) Does PostgreSQL have a graphical user interface?
Yes, there are several graphical interfaces to PostgreSQL available.
These include pgAdmin III (http://www.pgadmin.org, PgAccess
- http://www.pgaccess.org), RHDB Admin (http://sources.redhat.com/rhd b/
- ), TORA (http://www.globecom.net/tora/, partly commercial), and Rekall
- ( http://www.rekallrevealed.org/). There is also PhpPgAdmin (
+ http://www.pgaccess.org), RHDB Admin (http://sources.redhat.com/rhdb/
+ ), TORA ( http://www.globecom.net/tora/, partly commercial), and
+ Rekall ( http://www.rekallrevealed.org/). There is also PhpPgAdmin (
http://phppgadmin.sourceforge.net/ ), a web-based interface to
PostgreSQL.
expresssion index, it will be used:
CREATE INDEX tabindex ON tab (lower(col));
- 4.9) In a query, how do I detect if a field is NULL?
+ 4.9) In a query, how do I detect if a field is NULL? How can I sort on
+ whether a field is NULL or not?
You test the column with IS NULL and IS NOT NULL.
-
+ SELECT *
+ FROM tab
+ WHERE col IS NULL;
+
+ To sort by the NULL status, use the IS NULL and IS NOT NULL modifiers
+ in your WHERE clause. Things that are true will sort higher than
+ things that are false, so the following will put NULL entries at the
+ top of the resulting list:
+ SELECT *
+ FROM tab
+ ORDER BY (col IS NOT NULL)
+
4.10) What is the difference between the various character types?
Type Internal Name Notes
It is easy using set-returning functions,
http://techdocs.postgresql.org/guides/SetReturningFunctions.
- 4.20) Why can't I reliably create/drop temporary tables in PL/PgSQL
- functions?
+ 4.20) Why do I get "missing oid" errors when accessing temporary tables in
+ PL/PgSQL functions?
PL/PgSQL caches function scripts, and an unfortunate side effect is
that if a PL/PgSQL function accesses a temporary table, and that table
alink="#0000ff">
<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
- <P>Last updated: Wed Feb 2 12:44:03 EST 2005</P>
+ <P>Last updated: Thu Feb 24 19:33:07 EST 2005</P>
<P>Current maintainer: Bruce Momjian (<A href=
"mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)
searches and case-insensitive regular expression searches? How do I
use an index for case-insensitive searches?<BR>
<A href="#4.9">4.9</A>) In a query, how do I detect if a field
- is <SMALL>NULL</SMALL>?<BR>
+ is <SMALL>NULL</SMALL>? How can I sort on whether a field is <SMALL>
+ NULL</SMALL> or not?<BR>
<A href="#4.10">4.10</A>) What is the difference between the
various character types?<BR>
<A href="#4.11.1">4.11.1</A>) How do I create a
databases?<BR>
<A href="#4.19">4.19</A>) How do I return multiple rows or columns
from a function?<BR>
- <A href="#4.20">4.20</A>) Why can't I reliably create/drop
- temporary tables in PL/PgSQL functions?<BR>
+ <A href="#4.20">4.20</A>) Why do I get "missing oid" errors when
+ accessing temporary tables in PL/PgSQL functions?<BR>
<A href="#4.21">4.21</A>) What encryption options are available?<BR>
<P>PostgreSQL Data Base Management System</P>
<P>Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
- Portions Copyright (c) 1994-6 Regents of the University of California</P>
+ Portions Copyright (c) 1994-1996 Regents of the University of California</P>
<P>Permission to use, copy, modify, and distribute this software
and its documentation for any purpose, without fee, and without a
<H4><A name="1.4">1.4</A>) Where can I get PostgreSQL?</H4>
<P>The primary anonymous ftp site for PostgreSQL is <A href=
- "ftp://ftp.PostgreSQL.org/pub">ftp://ftp.PostgreSQL.org/pub</A>.
+ "ftp://ftp.PostgreSQL.org/pub/">ftp://ftp.PostgreSQL.org/pub/</A>.
For mirror sites, see our main web site.</P>
<H4><A name="1.5">1.5</A>) Where can I get support?</H4>
(<I>#postgresqlfr</I>). There is also a PostgreSQL channel on EFNet.
<P>A list of commercial support companies is available at <A href=
- "http://techdocs.postgresql.org/companies.php">http://techdocs.postg
- resql.org/companies.php</A>.</P>
+ "http://techdocs.postgresql.org/companies.php">
+ http://techdocs.postgresql.org/companies.php</A>.</P>
<H4><A name="1.6">1.6</A>) How do I submit a bug report?</H4>
http://www.postgresql.org/support/submitbug</A>.</P>
<P>Also check out our ftp site <A href=
- "ftp://ftp.PostgreSQL.org/pub">ftp://ftp.PostgreSQL.org/pub</A> to
+ "ftp://ftp.PostgreSQL.org/pub/">ftp://ftp.PostgreSQL.org/pub/</A> to
see if there is a more recent PostgreSQL version.</P>
<H4><A name="1.7">1.7</A>) What is the latest release?</H4>
</P>
<P>There are two PostgreSQL books available online at <A href=
- "http://www.PostgreSQL.org/docs/awbook.html">http://www.PostgreSQL.org/docs/awbook.html</A>
+ "http://www.postgresql.org/docs/books/awbook.html">http://www.postgresql.org/docs/books/awbook.html</A>
and <A href=
"http://www.commandprompt.com/ppbook/">http://www.commandprompt.com/ppbook/</A>.
There is a list of PostgreSQL books available for purchase at <A
<SMALL>SQL</SMALL>?</H4>
<P>The PostgreSQL book at <A href=
- "http://www.PostgreSQL.org/docs/awbook.html">http://www.PostgreSQL.org/docs/awbook.html</A>
+ "http://www.postgresql.org/docs/books/awbook.html">http://www.postgresql.org/docs/books/awbook.html</A>
teaches <SMALL>SQL</SMALL>. There is another PostgreSQL book at <A
href=
"http://www.commandprompt.com/ppbook/">http://www.commandprompt.com/ppbook.</A>
href="http://www.php.net">http://www.php.net</A>) is an excellent
interface.</P>
- <P>For complex cases, many use the Perl and CGI.pm or mod_perl.</P>
+ <P>For complex cases, many use the Perl DBD::Pg with CGI.pm or
+ mod_perl.</P>
<H4><A name="2.3">2.3</A>) Does PostgreSQL have a graphical user
interface?</H4>
href="http://www.pgadmin.org">http://www.pgadmin.org</a>, PgAccess
<a href="http://www.pgaccess.org"> http://www.pgaccess.org</a>),
RHDB Admin (<a
- href="http://sources.redhat.com/rhdb/">http://sources.redhat.com/rhd
- b/ </a>), TORA (<a
- href="http://www.globecom.net/tora/">http://www.globecom.net/tora/</a>,
- partly commercial), and Rekall (<a
+ href="http://sources.redhat.com/rhdb/">http://sources.redhat.com/rhdb/
+ </a>), TORA (<a href="http://www.globecom.net/tora/">
+ http://www.globecom.net/tora/</a>, partly commercial), and Rekall (<a
href="http://www.rekallrevealed.org/">
http://www.rekallrevealed.org/</a>). There is also PhpPgAdmin (<a
href="http://phppgadmin.sourceforge.net/">
</PRE>
<H4><A name="4.9">4.9</A>) In a query, how do I detect if a field
- is <SMALL>NULL</SMALL>?</H4>
+ is <SMALL>NULL</SMALL>? How can I sort on whether a field is <SMALL>
+ NULL</SMALL> or not?</H4>
<P>You test the column with <SMALL>IS NULL</SMALL> and <SMALL>IS
NOT NULL</SMALL>.</P>
+<PRE>
+ SELECT *
+ FROM tab
+ WHERE col IS NULL;
+</PRE>
+
+ <P>To sort by the <SMALL>NULL</SMALL> status, use the <SMALL>IS NULL</SMALL>
+ and <SMALL>IS NOT NULL</SMALL> modifiers in your <SMALL>WHERE</SMALL> clause.
+ Things that are <I>true</I> will sort higher than things that are <I>false</I>,
+ so the following will put NULL entries at the top of the resulting list:</P>
+
+<PRE>
+ SELECT *
+ FROM tab
+ ORDER BY (col IS NOT NULL)
+</PRE>
+
<H4><A name="4.10">4.10</A>) What is the difference between the
various character types?</H4>
<BLOCKQUOTE>
<a href="http://techdocs.postgresql.org/guides/SetReturningFunctions">
http://techdocs.postgresql.org/guides/SetReturningFunctions</a>.
- <H4><A name="4.20">4.20</A>) Why can't I reliably create/drop
- temporary tables in PL/PgSQL functions?</H4>
+ <H4><A name="4.20">4.20</A>) Why do I get "missing oid" errors when
+ accessing temporary tables in PL/PgSQL functions?</H4>
<P>PL/PgSQL caches function scripts, and an unfortunate side effect
is that if a PL/PgSQL function accesses a temporary table, and that
projects / thirdparty / postgresql.git / commitdiff
