STARTUP command fails : Why is that? I just installed Oracle Database Express Edition 11g Release 2.This is the first time I am using Oracle. Earlier I have used MySql and MSSql and I bet this one is a lot different !

These are the things I see in the start menu :



To start the oracle database, I click start database. Then in the prompt I do :

C:\Windows\system32&gt;SQLPLUS / AS SYSDBA

SQL*Plus: Release 11.2.0.2.0 Production on Sat Mar 2 20:37:14 2013

Copyright (c) 1982, 2010, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Express Edition Release 11.2.0.2.0 - Production

SQL&gt; STARTUP
ORA-01081: cannot start already-running ORACLE - shut it down first
SQL&gt;


I did exactly the same as written in DOCS but then why does I see that message as I run the command STARTUP.

Also certain commands like :


show databases;
use database db_name;


don't work in it ! Why is that ?

And isn't there a graphical query browser that comes packed with this RDMS ?
To restart Oracle, connect via SQL-PLUS as SYSDBA as you did previously, and type in the commands

shutdown normal;
startup mount;
alter database open;
exit;


Oracle SQL Developer can help you graphically administer the Oracle Database.

Most Oracle metadata are stored in special tables. For example,


To show all tables: select * from cat;
To show all users/schemas: select * from dab_users;
To change schemas: alter session set current_schema=NEW_SCHEMA_NAME;


Are there any other specific Oracle commands you were looking for?