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Diffstat (limited to 'doc/FAQ')
| -rw-r--r-- | doc/FAQ | 56 |
1 files changed, 36 insertions, 20 deletions
@@ -1,7 +1,7 @@ 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) @@ -59,7 +59,8 @@ 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? @@ -76,8 +77,8 @@ 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 @@ -119,7 +120,8 @@ 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 @@ -160,7 +162,8 @@ 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? @@ -177,14 +180,14 @@ 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? @@ -200,7 +203,7 @@ 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 @@ -220,9 +223,10 @@ 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. @@ -317,15 +321,15 @@ 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. @@ -633,10 +637,22 @@ 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 @@ -804,8 +820,8 @@ 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 |