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<!--
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/manage.sgml,v 1.21 2002/01/20 22:19:56 petere Exp $
-->
<Chapter Id="manage">
<Title>Managing a Database</Title>
<comment>
This section is currently a thinly disguised copy of the
Tutorial. Needs to be augmented.
- thomas 1998-01-12
</comment>
<Para>
Although the <FirstTerm>site administrator</FirstTerm> is responsible for overall management
of the <ProductName>PostgreSQL</ProductName> installation, some databases within the
installation may be managed by another person,
designated the <FirstTerm>database administrator</FirstTerm>.
This assignment of responsibilities occurs when a database is created.
A user may be assigned explicit privileges to create databases and/or to create new users.
A user assigned both privileges can perform most administrative tasks
within <ProductName>PostgreSQL</ProductName>, but will
not by default have the same operating system privileges as the site administrator.
</Para>
<Para>
The <citetitle>Administrator's Guide</> covers these topics in
more detail.
</Para>
<Sect1 id="db-creation">
<Title>Database Creation</Title>
<Para>
Databases are created by the <Command>CREATE DATABASE</Command>
command issued from within
<ProductName>PostgreSQL</ProductName>. <Application>createdb</Application>
is a shell script provided to give the same functionality from the
Unix command line.
</Para>
<Para>
The <ProductName>PostgreSQL</ProductName> backend must be running for either method
to succeed, and the user issuing the command must be the <ProductName>PostgreSQL</ProductName>
<FirstTerm>superuser</FirstTerm> or have been assigned database creation privileges by the
superuser.
</Para>
<Para>
To create a new database named <literal>mydb</literal> from the command line, type
<ProgramListing>
% createdb mydb
</ProgramListing>
and to do the same from within <Application>psql</Application> type
<ProgramListing>
=> CREATE DATABASE mydb;
</ProgramListing>
</Para>
<Para>
If you do not have the privileges required to create a database, you will see
the following:
<ProgramListing>
ERROR: CREATE DATABASE: Permission denied.
</ProgramListing>
</Para>
<Para>
You automatically become the
database administrator of the database you just created.
Database names must have an alphabetic first
character and are limited to 31 characters in length.
<ProductName>PostgreSQL</ProductName> allows you to create any number of
databases at a given site.
</Para>
<Para>
The <citetitle>Administrator's Guide</> discusses database creation
in more detail, including advanced options of the <command>CREATE
DATABASE</> command.
</Para>
</Sect1>
<Sect1 id="db-accessing">
<Title>Accessing a Database</Title>
<Para>
Once you have constructed a database, you can access it
by:
<itemizedlist spacing="compact" mark="bullet">
<listitem>
<para>
Running the <productname>PostgreSQL</productname> interactive
terminal program, called <application>psql</application>, which allows you
to interactively enter, edit, and execute
<acronym>SQL</acronym> commands.
</para>
</listitem>
<listitem>
<para>
Using an existing graphical frontend tool like
<application>PgAccess</application> or
<application>ApplixWare</application> (via
<acronym>ODBC</acronym>) to create and manipulate a database.
These possibilities are not covered in this tutorial.
</para>
</listitem>
<listitem>
<para>
Writing a custom application, using one of the several
available language bindings. These possibilities are discussed
further in <citetitle>The PostgreSQL Programmer's
Guide</citetitle>.
</para>
</listitem>
</itemizedlist>
You probably want to start up <Application>psql</Application>,
to try out the examples in this manual.
It can be activated for the <Database>mydb</Database>
database by typing the command:
<ProgramListing>
% psql mydb
</ProgramListing>
You will be greeted with the following message:
<ProgramListing>
Welcome to psql, the PostgreSQL interactive terminal.
Type: \copyright for distribution terms
\h for help with SQL commands
\? for help on internal slash commands
\g or terminate with semicolon to execute query
\q to quit
mydb=>
</ProgramListing>
</Para>
<Para>
This prompt indicates that <command>psql</command> is listening
to you and that you can type <Acronym>SQL</Acronym> queries into a
work space maintained by the terminal monitor.
The <Application>psql</Application> program itself responds to special
commands that begin
with the backslash character, <literal>\</literal>. For example, you
can get help on the syntax of various
<ProductName>PostgreSQL</ProductName> <Acronym>SQL</Acronym> commands by typing:
<ProgramListing>
mydb=> \h
</ProgramListing>
Once you have finished entering your queries into the
work space, you can pass the contents of the work space
to the <ProductName>PostgreSQL</ProductName> server by typing:
<ProgramListing>
mydb=> \g
</ProgramListing>
This tells the server to process the query. If you
terminate your query with a semicolon, the <literal>\g</literal> is not
necessary.
<Application>psql</Application> will automatically process semicolon terminated queries.
To read queries from a file, say <filename>myFile</filename>, instead of
entering them interactively, type:
<ProgramListing>
mydb=> \i myFile
</ProgramListing>
To get out of <Application>psql</Application> and return to Unix, type
<ProgramListing>
mydb=> \q
</ProgramListing>
and <Application>psql</Application> will quit and return you to your command
shell. (For more escape codes, type <Command>\?</Command> at the <command>psql</command>
prompt.)
White space (i.e., spaces, tabs and newlines) may be
used freely in <Acronym>SQL</Acronym> queries. Single-line comments are denoted by
<literal>--</literal>. Everything after the dashes up to the end of the
line is ignored. Multiple-line comments, and comments within a line,
are denoted by <literal>/* ... */</literal>.
</Para>
</Sect1>
<Sect1 id="db-destroy">
<Title>Destroying a Database</Title>
<Para>
If you are the owner of the database
<Database>mydb</Database>, you can destroy it using the SQL command
<ProgramListing>
=> DROP DATABASE mydb;
</ProgramListing>
or the Unix shell script
<ProgramListing>
% dropdb mydb
</ProgramListing>
This action physically removes all of the Unix files
associated with the database and cannot be undone, so
this should only be done with a great deal of forethought.
</Para>
</Sect1>
</Chapter>
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