|
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.
|
