Once you have created a database, you can access it by:
Running the PostgreSQL interactive
terminal program, called psql, which allows you
to interactively enter, edit, and execute
SQL commands.
Using an existing graphical frontend tool like
PgAccess or an office suite with
ODBC support to create and manipulate a
database. These possibilities are not covered in this
tutorial.
Writing a custom application, using one of the several
available language bindings. These possibilities are discussed
further in the PostgreSQL 7.3 Programmer's Guide.
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 7.3, 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
yourself. Being a superuser means that you are not subject to
access controls. For the purpose of this tutorial this is not of
importance.
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, and 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 7.3devel on i586-pc-linux-gnu, compiled by GCC 2.96
(1 row)
mydb=> SELECT current_date;
date
------------
2002-08-31
(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
PostgreSQL SQL
commands by typing:
mydb=> \h
To get out of psql, type
mydb=> \q
and psql will quit and return you to your
command shell. (For more internal commands, type
\? at the psql prompt.) The
full capabilities of psql are documented in
the PostgreSQL 7.3 Reference Manual. If PostgreSQL is
installed correctly you can also type man psql
at the operating system shell prompt to see the documentation. In
this tutorial we will not use these features explicitly, but you
can use them yourself when you see fit.
