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Backpatch FAQ entry for null concatenation.

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Bruce Momjian 2006-12-11 22:48:08 +00:00
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18
doc/FAQ
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@ -1,7 +1,7 @@
Frequently Asked Questions (FAQ) for PostgreSQL
Last updated: Sat Dec 2 07:15:34 EST 2006
Last updated: Mon Dec 11 17:45:54 EST 2006
Current maintainer: Bruce Momjian (bruce@momjian.us)
@ -59,8 +59,9 @@
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? How can I sort on
whether a field is NULL or not?
4.9) In a query, how do I detect if a field is NULL? How do I
concatenate possible NULLs? 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?
@ -631,15 +632,22 @@
upper and lowercase characters, it can not have identical values that
differ only in case. To force a particular case to be stored in the
column, use a CHECK constraint or a trigger.
4.9) In a query, how do I detect if a field is NULL? How do I
concatenate possible NULLs? How can I sort on whether a field is NULL
or not?
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?
4.9) In a query, how do I detect if a field is NULL? How do I concatenate
possible NULLs? How can I sort on whether a field is NULL or not?
You test the column with IS NULL and IS NOT NULL, like this:
SELECT *
FROM tab
WHERE col IS NULL;
To concatentate with possible NULLs, use COALESCE(), like this:
SELECT COALESCE(col1, '') || COALESCE(col2, '')
FROM tab
To sort by the NULL status, use the IS NULL and IS NOT NULL modifiers
in your ORDER BY clause. Things that are true will sort higher than
things that are false, so the following will put NULL entries at the

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doc/FAQ_AIX
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=======================================================
Frequently Asked Questions (FAQ) for PostgreSQL
AIX Specific
TO BE READ IN CONJUNCTION WITH THE NORMAL FAQ
=======================================================
Last updated: $Date: 2006/12/11 22:48:07 $
Topics
- AIX 4.3.2 Port Report
- AIX 5.3 Additional Information
- AIX, readline, and postgres 8.1.x:
- AIX Memory Management: An Overview
- Statistics Collector Fun on AIX
-----
From: Zeugswetter Andreas <ZeugswetterA@spardat.at>
$Date: 2006/09/20 02:10:11 $
$Date: 2006/12/11 22:48:07 $
On AIX 4.3.2 PostgreSQL compiled with the native IBM compiler xlc
(vac.C 5.0.1) passes all regression tests. Other versions of OS and

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doc/FAQ_HPUX
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=======================================================
Frequently Asked Questions (FAQ) for PostgreSQL 7.3
Frequently Asked Questions (FAQ) for PostgreSQL
HP-UX Specific
TO BE READ IN CONJUNCTION WITH THE NORMAL FAQ
=======================================================
last updated: $Date: 2006/07/19 02:37:00 $
last updated: $Date: 2006/12/11 22:48:07 $
current maintainer: Tom Lane (tgl@sss.pgh.pa.us)
original author: Tom Lane (tgl@sss.pgh.pa.us)
@ -21,7 +21,7 @@ Section 1: Installing PostgreSQL
1.1) What do I need to install PostgreSQL on HP-UX?
PostgreSQL 7.3 should work on Series 700/800 PA-RISC machines running
PostgreSQL 7.3+ should work on Series 700/800 PA-RISC machines running
HP-UX 10.X or 11.X, given appropriate system patch levels and build
tools. At least one developer routinely tests on HPUX 10.20 and we
have reports of successful installations on HPUX 11.00 and 11.11.

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doc/FAQ_IRIX
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@ -3,7 +3,7 @@ Frequently Asked Questions (FAQ) for PostgreSQL
IRIX Specific
TO BE READ IN CONJUNCTION WITH THE NORMAL FAQ
=======================================================
last updated: $Date: 2002/11/11 20:04:05 $
last updated: $Date: 2006/12/11 22:48:07 $
current maintainer: Luis Amigo (lamigo@atc.unican.es)
original author: Luis Amigo (lamigo@atc.unican.es)

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doc/FAQ_MINGW
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@ -8,14 +8,14 @@
The most recent version of this document can be viewed at
http://www.postgresql.org/docs/faqs.FAQ_MINGW.html.
The FAQ for running PostgreSQL on native Win32 is at
http://pginstaller.projects.postgresql.org/FAQ_windows.html.
The FAQ Running & Installing PostgreSQL On Native Windows is at
http://pginstaller.projects.postgresql.org/faq/FAQ_windows.html.
The native Win32 port is built from source using MinGW tools. There
is also a precompiled binary installer called pginstaller which you
can find at from http://pgfoundry.org/projects/pginstaller. It is a
fully native build and uses no additional software like MinGW. The
ready-made instlaler files are available on the main PostgreSQL ftp
ready-made installer files are available on the main PostgreSQL ftp
servers in the binary/win32 directory.
Tools for Building Binaries

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doc/FAQ_SCO
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============================================================
Frequently Asked Questions (FAQ) for PostgreSQL 7.3
SCO UnixWare and OpenServer specific
to be read in conjunction with the installation instructions
============================================================
last updated: $Date: 2004/08/04 21:33:39 $
=======================================================
Frequently Asked Questions (FAQ) for PostgreSQL
IRIX Specific
TO BE READ IN CONJUNCTION WITH THE NORMAL FAQ
=======================================================
last updated: $Date: 2006/12/11 22:48:07 $
current maintainer: Billy G. Allie (Bill.Allie@mug.org)
original author: Andrew Merrill (andrew@compclass.com)
Consult http://buildfarm.postgresql.org/ for latest information.
PostgreSQL 8.0 can be built on SCO UnixWare 7 and SCO OpenServer 5.
On OpenServer, you can use either the OpenServer Development Kit or
the Universal Development Kit.

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doc/FAQ_Solaris
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@ -3,7 +3,7 @@ Frequently Asked Questions (FAQ) for PostgreSQL
Sun Solaris specific
To be read in conjunction with the installation instructions.
============================================================
Last updated: $Date: 2006/12/03 16:43:05 $
Last updated: $Date: 2006/12/11 22:48:07 $
Contents:

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doc/src/FAQ/FAQ.html
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@ -10,7 +10,7 @@
alink="#0000ff">
<H1>Frequently Asked Questions (FAQ) for PostgreSQL</H1>
<P>Last updated: Sat Dec 2 07:15:34 EST 2006</P>
<P>Last updated: Mon Dec 11 17:45:54 EST 2006</P>
<P>Current maintainer: Bruce Momjian (<A href=
"mailto:bruce@momjian.us">bruce@momjian.us</A>)
@ -86,8 +86,8 @@
searches and case-insensitive regular expression searches? How do I
use an index for case-insensitive searches?<BR>
<A href="#item4.9">4.9</A>) In a query, how do I detect if a field
is <SMALL>NULL</SMALL>? How can I sort on whether a field is <SMALL>
NULL</SMALL> or not?<BR>
is <SMALL>NULL</SMALL>? How do I concatenate possible <SMALL>NULL</SMALL>s?
How can I sort on whether a field is <SMALL> NULL</SMALL> or not?<BR>
<A href="#item4.10">4.10</A>) What is the difference between the
various character types?<BR>
<A href="#item4.11.1">4.11.1</A>) How do I create a
@ -824,9 +824,13 @@ table?</TD><TD>unlimited</TD></TR>
case to be stored in the column, use a <SMALL>CHECK</SMALL>
constraint or a trigger.</P>
<A href="#item4.9">4.9</A>) In a query, how do I detect if a field
is <SMALL>NULL</SMALL>? How do I concatenate possible <SMALL>NULL</SMALL>s?
How can I sort on whether a field is <SMALL> NULL</SMALL> or not?<BR>
<H3 id="item4.9">4.9) In a query, how do I detect if a field
is <SMALL>NULL</SMALL>? How can I sort on whether a field is <SMALL>
NULL</SMALL> or not?</H3>
is <SMALL>NULL</SMALL>? How do I concatenate possible <SMALL>NULL</SMALL>s?
How can I sort on whether a field is <SMALL> NULL</SMALL> or not?</H3>
<P>You test the column with <SMALL>IS NULL</SMALL> and <SMALL>IS
NOT NULL</SMALL>, like this:</P>
@ -837,6 +841,13 @@ table?</TD><TD>unlimited</TD></TR>
WHERE col IS NULL;
</PRE>
<P>To concatentate with possible <SMALL>NULL</SMALL>s, use <I>COALESCE()</I>,
like this:</P>
<PRE>
SELECT COALESCE(col1, '') || COALESCE(col2, '')
FROM tab
</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>ORDER BY</SMALL> clause.
Things that are <I>true</I> will sort higher than things that are <I>false</I>,
@ -1091,7 +1102,7 @@ length</TD></TR>
double-quotes around table or column names during table creation.
When double-quotes are used, table and column names (called
identifiers) are stored <a
href="http://www.postgresql.org/docs/8.2/static/sql-syntax.html#SQL-SYNTAX-IDENTIFIERS">
href="http://www.postgresql.org/docs/current/static/sql-syntax.html#SQL-SYNTAX-IDENTIFIERS">
case-sensitive</a>, meaning you must use double-quotes when
referencing the names in a query. Some interfaces, like pgAdmin,
automatically double-quote identifiers during table creation.

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doc/src/sgml/ref/psql-ref.sgml
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<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.175.2.2 2006/12/06 15:40:32 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.175.2.3 2006/12/11 22:48:08 momjian Exp $
PostgreSQL documentation
-->
@ -89,7 +89,7 @@ PostgreSQL documentation
<acronym>SQL</acronym> and <application>psql</application>
meta-commands with this option. To achieve that, you could
pipe the string into <application>psql</application>, like
this: <literal>echo "\x \\ SELECT * FROM foo;" | psql</literal>.
this: <literal>echo '\x \\ SELECT * FROM foo;' | psql</literal>.
(<literal>\\</> is the separator meta-command.)
</para>
<para>