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><H1
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><A
NAME="TUTORIAL-CREATEDB"
>1.3. Creating a Database</A
></H1
><P
> The first test to see whether you can access the database server
is to try to create a database. A running
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> server can manage many
databases. Typically, a separate database is used for each
project or for each user.
</P
><P
> Possibly, your site administrator has already created a database
for your use. He should have told you what the name of your
database is. In that case you can omit this step and skip ahead
to the next section.
</P
><P
> To create a new database, in this example named
<TT
CLASS="LITERAL"
>mydb</TT
>, you use the following command:
</P><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>createdb mydb</KBD
></PRE
><P>
If this produces no response then this step was successful and you can skip over the
remainder of this section.
</P
><P
> If you see a message similar to:
</P><PRE
CLASS="SCREEN"
>createdb: command not found</PRE
><P>
then <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> was not installed properly. Either it was not
installed at all or your shell's search path was not set to include it.
Try calling the command with an absolute path instead:
</P><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>/usr/local/pgsql/bin/createdb mydb</KBD
></PRE
><P>
The path at your site might be different. Contact your site
administrator or check the installation instructions to
correct the situation.
</P
><P
> Another response could be this:
</P><PRE
CLASS="SCREEN"
>createdb: could not connect to database postgres: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/tmp/.s.PGSQL.5432"?</PRE
><P>
This means that the server was not started, or it was not started
where <TT
CLASS="COMMAND"
>createdb</TT
> expected it. Again, check the
installation instructions or consult the administrator.
</P
><P
> Another response could be this:
</P><PRE
CLASS="SCREEN"
>createdb: could not connect to database postgres: FATAL: role "joe" does not exist</PRE
><P>
where your own login name is mentioned. This will happen if the
administrator has not created a <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> user account
for you. (<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> user accounts are distinct from
operating system user accounts.) If you are the administrator, see
<A
HREF="user-manag.html"
>Chapter 20</A
> for help creating accounts. You will need to
become the operating system user under which <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>
was installed (usually <TT
CLASS="LITERAL"
>postgres</TT
>) to create the first user
account. It could also be that you were assigned a
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> user name that is different from your
operating system user name; in that case you need to use the <TT
CLASS="OPTION"
>-U</TT
>
switch or set the <TT
CLASS="ENVAR"
>PGUSER</TT
> environment variable to specify your
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> user name.
</P
><P
> If you have a user account but it does not have the privileges required to
create a database, you will see the following:
</P><PRE
CLASS="SCREEN"
>createdb: database creation failed: ERROR: permission denied to create database</PRE
><P>
Not every user has authorization to create new databases. If
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> refuses to create databases
for you then the site administrator needs to grant you permission
to create databases. Consult your site administrator if this
occurs. If you installed <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>
yourself then you should log in for the purposes of this tutorial
under the user account that you started the server as.
<A
NAME="AEN473"
HREF="#FTN.AEN473"
><SPAN
CLASS="footnote"
>[1]</SPAN
></A
>
</P
><P
> You can also create databases with other names.
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> allows you to create any
number of databases at a given site. Database names must have an
alphabetic first character and are limited to 63 bytes in
length. A convenient choice is to create a database with the same
name as your current user name. Many tools assume that database
name as the default, so it can save you some typing. To create
that database, simply type:
</P><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>createdb</KBD
></PRE
><P>
</P
><P
> If you do not want to use your database anymore you can remove it.
For example, if you are the owner (creator) of the database
<TT
CLASS="LITERAL"
>mydb</TT
>, you can destroy it using the following
command:
</P><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>$</SAMP
> <KBD
CLASS="USERINPUT"
>dropdb mydb</KBD
></PRE
><P>
(For this command, the database name does not default to the user
account name. You always need to specify it.) This action
physically removes all files associated with the database and
cannot be undone, so this should only be done with a great deal of
forethought.
</P
><P
> More about <TT
CLASS="COMMAND"
>createdb</TT
> and <TT
CLASS="COMMAND"
>dropdb</TT
> can
be found in <A
HREF="app-createdb.html"
><SPAN
CLASS="APPLICATION"
>createdb</SPAN
></A
> and <A
HREF="app-dropdb.html"
><SPAN
CLASS="APPLICATION"
>dropdb</SPAN
></A
>
respectively.
</P
></DIV
><H3
CLASS="FOOTNOTES"
>Notes</H3
><TABLE
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><A
NAME="FTN.AEN473"
HREF="tutorial-createdb.html#AEN473"
><SPAN
CLASS="footnote"
>[1]</SPAN
></A
></TD
><TD
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><P
> As an explanation for why this works:
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> user names are separate
from operating system user accounts. When you connect to a
database, you can choose what
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> user name to connect as;
if you don't, it will default to the same name as your current
operating system account. As it happens, there will always be a
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> user account that has the
same name as the operating system user that started the server,
and it also happens that that user always has permission to
create databases. Instead of logging in as that user you can
also specify the <TT
CLASS="OPTION"
>-U</TT
> option everywhere to select
a <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> user name to connect as.
</P
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