21.2. Creating a Database #
In order to create a database, the Postgres Pro server must be up and running (see Section 17.3).
Databases are created with the SQL command CREATE DATABASE:
CREATE DATABASE name
;
where name
follows the usual rules for SQL identifiers. The current role automatically becomes the owner of the new database. It is the privilege of the owner of a database to remove it later (which also removes all the objects in it, even if they have a different owner).
The creation of databases is a restricted operation. See Section 20.2 for how to grant permission.
Since you need to be connected to the database server in order to execute the CREATE DATABASE
command, the question remains how the first database at any given site can be created. The first database is always created by the initdb
command when the data storage area is initialized. (See Section 17.2.) This database is called postgres
. So to create the first “ordinary” database you can connect to postgres
.
Two additional databases, template1
and template0
, are also created during database cluster initialization. Whenever a new database is created within the cluster, template1
is essentially cloned. This means that any changes you make in template1
are propagated to all subsequently created databases. Because of this, avoid creating objects in template1
unless you want them propagated to every newly created database. template0
is meant as a pristine copy of the original contents of template1
. It can be cloned instead of template1
when it is important to make a database without any such site-local additions. More details appear in Section 21.3.
As a convenience, there is a program you can execute from the shell to create new databases, createdb
.
createdb dbname
createdb
does no magic. It connects to the postgres
database and issues the CREATE DATABASE
command, exactly as described above. The createdb reference page contains the invocation details. Note that createdb
without any arguments will create a database with the current user name.
Note
Chapter 19 contains information about how to restrict who can connect to a given database.
Sometimes you want to create a database for someone else, and have them become the owner of the new database, so they can configure and manage it themselves. To achieve that, use one of the following commands:
CREATE DATABASEdbname
OWNERrolename
;
from the SQL environment, or:
createdb -Orolename
dbname
from the shell. Only the superuser is allowed to create a database for someone else (that is, for a role you are not a member of).