1.3. Creating a Database#
The first test to see whether you can access the database server is to try to create a database. A runningPostgres Pro 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. In that case you can omit this step and skip ahead to the next section.
To create a new database, in this example namedmydb, you use the following command:
$createdb mydb
If this produces no response then 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
thenPostgres Pro 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:
$/usr/local/pgsql/bin/createdb mydb
The path at your site might be different. Contact your site administrator or check the installation instructions to correct the situation.
Another response could be this:
createdb: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such file or directory Is the server running locally and accepting connections on that socket?
This means that the server was not started, or it is not listening wherecreatedb expects to contact it. Again, check the installation instructions or consult the administrator.
Another response could be this:
createdb: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: FATAL: role "joe" does not exist
where your own login name is mentioned. This will happen if the administrator has not created aPostgres Pro user account for you. (Postgres Pro user accounts are distinct from operating system user accounts.) If you are the administrator, seeChapter 20 for help creating accounts. You will need to become the operating system user under whichPostgres Pro was installed (usuallypostgres) to create the first user account. It could also be that you were assigned aPostgres Pro user name that is different from your operating system user name; in that case you need to use the-U switch or set thePGUSER environment variable to specify yourPostgres Pro user name.
If you have a user account but it does not have the privileges required to create a database, you will see the following:
createdb: error: database creation failed: ERROR: permission denied to create database
Not every user has authorization to create new databases. IfPostgres Pro 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 installedPostgres Pro yourself then you should log in for the purposes of this tutorial under the user account that you started the server as.[1]
You can also create databases with other names.Postgres Pro 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:
$createdb
If you do not want to use your database anymore you can remove it. For example, if you are the owner (creator) of the databasemydb, 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.
More aboutcreatedb anddropdb can be found increatedb anddropdb respectively.
[1] As an explanation for why this works:Postgres Pro user names are separate from operating system user accounts. When you connect to a database, you can choose whatPostgres Pro 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 aPostgres Pro 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-U option everywhere to select aPostgres Pro user name to connect as.