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11 KiB
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<TITLE>The POSTGRES95 User Manual - GETTING STARTED</TITLE>
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<A HREF="pg95user.html">[ TOC ]</A>
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<H1>3. GETTING STARTED WITH POSTGRES</H1>
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<HR>
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This section discusses how to start POSTGRES and set up
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your own environment so that you can use frontend
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applications. We assume POSTGRES has already been
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successfully installed. (Refer to the installation notes
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for how to install POSTGRES.)
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<p>
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Some of the steps listed in this section will apply to
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all POSTGRES users, and some will apply primarily to
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the site database administrator. This site administrator
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is the person who installed the software, created
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the database directories and started the <B>postmaster</B>
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process. This person does not have to be the UNIX
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superuser, "root," or the computer system administrator.
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In this section, items for end users are labelled
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"User" and items intended for the site administrator
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are labelled "Admin."
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Throughout this manual, any examples that begin with
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the character ``%'' are commands that should be typed
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at the UNIX shell prompt. Examples that begin with the
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character ``*'' are commands in the POSTGRES query
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language, POSTGRES <B>SQL</B>.
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<H2><A NAME="setting-up-your-environment">3.1. Admin/User: Setting Up Your Environment</A></H2>
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<IMG SRC="figure02.gif" ALT="Figure 2. POSTGRES file layout.">
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Figure 2. shows how the POSTGRES distribution is laid
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out when installed in the default way. For simplicity,
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we will assume that POSTGRES has been installed in the
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directory /usr/local/postgres95. Therefore, wherever
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you see the directory /usr/local/postgres95 you should
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substitute the name of the directory where POSTGRES is
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actually installed.
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All POSTGRES commands are installed in the directory
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/usr/local/postgres95/bin. Therefore, you should add
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this directory to your shell command path. If you use
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a variant of the Berkeley C shell, such as csh or tcsh,
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you would add
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<pre> % set path = ( /usr/local/postgres95/bin $path )
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</pre>
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in the .login file in your home directory. If you use
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a variant of the Bourne shell, such as sh, ksh, or
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bash, then you would add
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<pre>
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% PATH=/usr/local/postgres95/bin:$PATH
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% export PATH
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</pre>
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to the .profile file in your home directory.
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From now on, we will assume that you have added the
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POSTGRES bin directory to your path. In addition, we
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will make frequent reference to "setting a shell
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variable" or "setting an environment variable" throughout
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this document. If you did not fully understand the
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last paragraph on modifying your search path, you
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should consult the UNIX manual pages that describe your
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shell before going any further.
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<H2><A NAME="starting-the-postmaster">3.2. Admin: Starting the <B>Postmaster</A></B></H2>
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It should be clear from the preceding discussion that
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nothing can happen to a database unless the <B>postmaster</B>
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process is running. As the site administrator, there
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are a number of things you should remember before
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starting the <B>postmaster</B>. These are discussed in the
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section of this manual titled, "Administering POSTGRES."
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However, if POSTGRES has been installed by following
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the installation instructions exactly as written, the
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following simple command is all you should
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need to start the <B>postmaster</B>:
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<pre> % postmaster &
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</pre>
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The <B>postmaster</B> occasionally prints out messages which
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are often helpful during troubleshooting. If you wish
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to view debugging messages from the <B>postmaster</B>, you can
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start it with the -d option and redirect the output to
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the log file:
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<pre> % postmaster -d >& pm.log &
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</pre>
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If you do not wish to see these messages, you can type
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<pre> % postmaster -S
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</pre>
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and the <B>postmaster</B> will be "S"ilent. Notice that there
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is no ampersand ("&") at the end of the last example.
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<H2><A NAME="adding-and-deleting-users">3.3. Admin: Adding and Deleting Users</A></H2>
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The createuser command enables specific users to access
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POSTGRES. The destroyuser command removes users and
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prevents them from accessing POSTGRES. Note that these
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commands only affect users with respect to POSTGRES;
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they have no effect administration of users that the
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operating system manages.
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<H2><A NAME="starting-applications">3.4. User: Starting Applications</A></H2>
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Assuming that your site administrator has properly
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started the <B>postmaster</B> process and authorized you to
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use the database, you (as a user) may begin to start up
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applications. As previously mentioned, you should add
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/usr/local/postgres95/bin to your shell search path.
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In most cases, this is all you should have to do in
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terms of preparation.<A HREF="#1">1</A>
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If you get the following error message from a POSTGRES
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command (such as <B>psql</B> or createdb):
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<pre> connectDB() failed: Is the postmaster running at 'localhost' on port '4322'?
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</pre>
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it is usually because (1) the <B>postmaster</B> is not running, or (2) you are attempting to connect to the wrong
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server host.
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If you get the following error message:
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<pre> FATAL 1:Feb 17 23:19:55:process userid (2360) !=
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database owner (268)
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</pre>
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it means that the site administrator started the <B>postmaster</B> as the wrong user. Tell him to restart it as
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the POSTGRES superuser.
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<H2><A NAME="managing-a-database">3.5. User: Managing a Database</A></H2>
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Now that POSTGRES is up and running we can create some
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databases to experiment with. Here, we describe the
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basic commands for managing a database.
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<H3><A NAME="creating-a-database">3.5.1. Creating a Database</A></H3>
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Let's say you want to create a database named mydb.
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You can do this with the following command:
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<pre> % createdb mydb
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</pre>
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POSTGRES allows you to create any number of databases
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at a given site and you automatically become the
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database administrator of the database you just created. Database names must have an alphabetic first
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character and are limited to 16 characters in length.
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Not every user has authorization to become a database
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administrator. If POSTGRES refuses to create databases
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for you, then the site administrator needs to grant you
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permission to create databases. Consult your site
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administrator if this occurs.
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<H3><A NAME="accessing-a-database">3.5.2. Accessing a Database</A></H3>
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Once you have constructed a database, you can access it
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by:
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<UL>
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<LI>running the POSTGRES terminal monitor programs (
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monitor or <B>psql</B>) which allows you to interactively
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enter, edit, and execute <B>SQL</B> commands.
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<LI>writing a C program using the LIBPQ subroutine
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library. This allows you to submit <B>SQL</B> commands
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from C and get answers and status messages back to
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your program. This interface is discussed further
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in section ??.
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</UL>
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You might want to start up <B>psql</B>, to try out the examples in this manual. It can be activated for the mydb
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database by typing the command:
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<pre> % psql mydb
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</pre>
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You will be greeted with the following message:
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<pre> Welcome to the POSTGRES95 interactive sql monitor:
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type \? for help on slash commands
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type \q to quit
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type \g or terminate with semicolon to execute query
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You are currently connected to the database: mydb
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mydb=>
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</pre> This prompt indicates that the terminal monitor is listening to you and that you can type <B>SQL</B> queries into a
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workspace maintained by the terminal monitor.
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The <B>psql</B> program responds to escape codes that begin
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with the backslash character, "\". For example, you
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can get help on the syntax of various POSTGRES <B>SQL</B> commands by typing:
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<pre> mydb=> \h
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</pre>
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Once you have finished entering your queries into the
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workspace, you can pass the contents of the workspace
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to the POSTGRES server by typing:
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<pre> mydb=> \g
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</pre>
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This tells the server to process the query. If you
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terminate your query with a semicolon, the \g is not
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necessary. <B>psql</B> will automatically process semicolon terminated queries.
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To read queries from a file, say myFile, instead of
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entering them interactively, type:
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<pre> mydb=> \i fileName
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</pre>
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To get out of <B>psql</B> and return to UNIX, type
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<pre> mydb=> \q
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</pre>
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and <B>psql</B> will quit and return you to your command
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shell. (For more escape codes, type \h at the monitor
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prompt.)
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White space (i.e., spaces, tabs and newlines) may be
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used freely in <B>SQL</B> queries. Comments are denoted by
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<b>--</b>. Everything after the dashes up to the end of the
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line is ignored.
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<H3><A NAME="detroying-a-database">3.5.3. Destroying a Database</A></H3>
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If you are the database administrator for the database
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mydb, you can destroy it using the following UNIX command:
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<pre> % destroydb mydb
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</pre>
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This action physically removes all of the UNIX files
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associated with the database and cannot be undone, so
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this should only be done with a great deal of fore-thought.
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<p>
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<HR>
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<A NAME="1"><B>1.</B></A> If your site administrator has not set things up in the
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default way, you may have some more work to do. For example, if the database server machine is a remote machine, you
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will need to set the <B>PGHOST</B> environment variable to the name
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of the database server machine. The environment variable
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<B>PGPORT</B> may also have to be set. The bottom line is this: if
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you try to start an application program and it complains
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that it cannot connect to the <B>postmaster</B>, you should immediately consult your site administrator to make sure that your
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environment is properly set up.
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<HR>
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<font size=-1>
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<A HREF="pg95user.html">[ TOC ]</A>
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<A HREF="architec.html">[ Previous ]</A>
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<A HREF="query.html">[ Next ]</A>
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