Accessing a Database

Once you have created a database, you can access it by:

You probably want to start up psql to try out the examples in this tutorial. It can be activated for the mydb database by typing the command:
$ psql mydb
If you leave off the database name then it will default to your user account name. You already discovered this scheme in the previous section.

In psql, you will be greeted with the following message:
Welcome to psql, the PostgreSQL interactive terminal.
 
Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help on internal slash commands
       \g or terminate with semicolon to execute query
       \q to quit
 
mydb=>
The last line could also be:
mydb=#
That would mean you are a database superuser, which is most likely the case if you installed PostgreSQL from source code. Being a superuser means that you are not subject to access controls. For the purpose of this tutorial this is not important.

If you have encountered problems starting psql then go back to the previous section. The diagnostics of psql and createdb are similar, and if the latter worked the former should work as well.

The last line printed out by psql is the prompt. It indicates that psql is listening to you and that you can type SQL queries into a work space maintained by psql. Try out these commands:
mydb=> SELECT version();
                            version
----------------------------------------------------------------
 PostgreSQL 7.2.2-RH on i686-pc-linux-gnu, compiled by GCC 2.96
(1 row)

mydb=> SELECT current_date;
    date
------------
 2002-09-04
(1 row)

mydb=> SELECT 2 + 2;
 ?column?
----------
        4
(1 row)

The psql program has a number of internal commands that are not SQL commands. They begin with the backslash character, "\". Some of these commands were listed in the welcome message. For example, you can get help on the syntax of various SQL commands by typing:
mydb=> \h

To quit psql, type
mydb=> \q
psql will exit and return you to your command shell. The full capabilities of psql are documented in the the reference section of this manual. You can also type man psql at your shell prompt to see the documentation.