The first test to see whether you can access the database server
is to try to create a database. A running
PostgreSQL server can manage many
databases. Typically, a separate database is used for each
project or for each user.
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 this case you can omit this step and skip ahead
to the next section.
To create a new database, in this example named
mydb, you use the following command:
$ createdb mydb
This should produce as response:
CREATE DATABASE
If so, this step was successful and you can skip over the
remainder of this section.
If you see a message similar to
createdb: command not found
then PostgreSQL was not installed properly. Either it was not
installed at all or the search path was not set correctly. Try
calling the command with an absolute path instead:
$ /usr/local/pgsql/bin/createdb mydb
The path at your site might be different. Contact your site
administrator or check back in the installation instructions to
correct the situation.
Another response could be this:
psql: could not connect to server: Connection refused
Is the server running locally and accepting
connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
createdb: database creation failed
This means that the server was not started, or it was not started
where createdb expected it. Again, check the
installation instructions or consult the administrator.
If you do not have the privileges required to create a database,
you will see the following:
ERROR: CREATE DATABASE: permission denied
createdb: database creation failed
Not every user has authorization to create new databases. If
PostgreSQL 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 PostgreSQL
yourself then you should log in for the purposes of this tutorial
under the user account that you started the server as.
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You can also create databases with other names.
PostgreSQL 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 characters 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
$ createdb
If you don't want to use your database anymore you can remove it.
For example, if you are the owner (creator) of the database
mydb, you can destroy it using the following
command:
$ dropdb mydb
(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.
