How To Get A List Of Oracle Database Schemas?

Well, this is one of those circumstances, where your ability to answer this question will depend upon your user’s assigned security roles and what you actually want. 

To get a complete list, you will need to use the DBA_ administrator tables to which most of us will not have access.  In the very simple examples below, you may want to add a WHERE clause to eliminate the system schemas from the list, like ‘SYS’ and ‘SYSTEM,’ if you have access to them.

Example Administrator (DBA) Schema List

SELECT distinct OWNER as SCHEMA_NAME

FROM  DBA_OBJECTS

ORDER BY OWNER;

Example Administrator (DBA) Schema List Results Screenshot

Fortunately for the rest of us, there are All user tables, from which we can get a listing of the schemas to which we have access.

Example All Users Schema List

SELECT distinct OWNER as SCHEMA_NAME

FROM    ALL_OBJECTS

ORDER BY OWNER;

Example All Users Schema List Results Screenshot

Related References

Oracle help Center > Database> Oracle > Oracle Database > Release 19

https://docs.oracle.com/en/database/oracle/oracle-database/19/cncpt/data-dictionary-and-dynamic-performance-views.html#GUID-BDF5B748-EB43-4B48-938E-89099069C3BB

Oracle SQL*Plus Is still Around

It is funny how you cannot work with some for a while because of newer tools, and then rediscover them, so to speak.  The other day I was looking at my overflow bookshelf in the garage and saw an old book on Oracle SQL*Plus and was thinking, “do I still want or need that book?”. 

In recent years I have been using a variety of other tools when working with oracle. So, I really hadn’t thought about the once ubiquitous Oracle SQL*Plus command-line interface for Oracle databases, which around for thirty-five years or more.  However, I recently needed to do an Oracle 18C database install to enable some training and was pleasantly surprised Oracle SQL*Plus as a menu item. 

Now I have been purposely using Oracle SQL*Plus again to refresh my skills, and I will be keeping my Oracle SQL*Plus: The Definitive Guide, after all. 

How to Determine Your Oracle Database Name

Oracle provides a few ways to determine which database you are working in.  Admittedly, I usually know which database I’m working in, but recently I did an Oracle Database Express Edition (XE) install which did not goes has expected and I had reason to confirm which database I was actually in when the SQL*Plus session opened.  So, this lead me to consider how one would prove exactly which database they were connected to.  As it happens, Oracle has a few ways to quickly display which database you are connected to and here are two easy ways to find out your Oracle database name in SQL*Plus:

  • V$DATABASE
  • GLOBAL_NAME

Checking the GLOBAL_NAME table

The First method is to run a quick-select against the GLOBAL_NAME table, which. is publicly available to logged-in users of the database

Example GLOBAL_NAME Select Statement

select * from global_name;

Checking the V$DATABASE Variable

The second method is to run a quick-select a V$database. However, not everyone will have access to the V$database variable.

Example V$database Select Statement

select name from V$database;

Linux VI Command – Set Line Number

The “Set Number” command in the VI (visual instrument) text editor seems may not seem like the most useful command.  However, it is more useful than it appears.  Using the “set number” command is a visual aid, which facilitates navigation within the VI editor. 

To Enable Line Number In the VI Editor

The “set Number” command is used to make display line numbers, to enable line numbers:

  • Press the Esc key within the VI editor, if you are currently in insert or append mode.
  • Press the colon key “:”, which will appear at the lower-left corner of the screen.
  • Following the colon enter “set number” command (without quotes) and press enter.

A column of sequential line numbers will then appear at the left side of the screen. Each line number references the text located directly to the right. Now you will know exactly which line is where and be able to enter a colon and the line number you want to move to and move around the document lines with certainty.

To Disable Line Number In the VI Editor

When you are ready to turn offline numbering, again follow the preceding instructions, except this time, enter the following line at the : prompt:

  • Press the Esc key within the VI editor, if you are currently in insert or append mode.
  • Press the colon key “:”, which will appear at the lower-left corner of the screen.
  • Following the colon enter “set nonumber” command (without quotes) and press enter.

To Make The Line Number Enable When You Open VI:

Normally, vi will forget the setting you’ve chosen once you’ve left the editor. You can, however, make the “set Number” command take effect automatically whenever you use vi on a user/account, enter the “set Number” command as a line in the .exrc file in your home directory.

Related References

Useful Links – Linux

Here are a few useful references for Linux, which may be helpful.

Linux Documentation

Bash Documentation

Links for Major Linux Distributions

CentOS

Red Hat Enterprise Linux (RHEL)

Ubuntu

The most Important Linux Distributions To Learn Professionally

Many of us either want a way to import our Linux knowledge, improve our technical career options or perhaps, move into the technology career.  To do any of these efficiently them, the first step would be to focus on the major Linux distribution used by employers. 

The most adapted distributions Linux are Red Hat Enterprise Linux (RHEL) and Ubuntu, so, of the multitude of Linux distributions available, these would be the to learn if you want to move your career forward.

However, if you are seeking an inexpensive alternative to hone your Linux skills at home, then CentOS, is likely your best choice since it is free and is pretty much a copy of RedHat.

Related References

Best Linux Distros for Beginners

For those people who dip their toe into Linux systems for the first time, the endless options for distributions can be overwhelming, mainly when you are unsure for what to search. Just a few years ago when Linux was still in its early stages, this task would be much more comfortable as you could choose one of which you have heard about or have experienced. However, the increasing number of available distros and their vocal fans makes it challenging to settle on one.
So if you are new to this platform and don’t know where to start, here are top 5 best Linux distros for beginners to check out.

CentOS is a Linux distribution, which is derived from the sources of Red Hat Enterprise Linux and therefore has an obvious advantage for folks wanting to learn, improve, and practice their skills. Especially, since it is a free distribution and there are courses available to get you started on training sites like Udemy. the relationship between CentOS and Rehat make the skill and commands learn transferable since Redhat is a major Linux distribution us by businesses.

Ubuntu Linux

A list of Linux distros can’t be complete without the Ubuntu Linux. Indeed, most Linux distros come from Ubuntu simply because it is among the most user-friendly and stable ones available.
Just like other modern systems, Ubuntu Linux includes its app store named Ubuntu Software. You can find a collection of numerous apps to install. Though they might look entirely unfamiliar at the beginning, any mobile or computer user would learn how to use it quickly without a learning curve.
Ubuntu Linux comes with the installed software, which may include the web browser Firefox, office suite LibreOffice, webcam app Cheese, email client Thunderbird, and more.

Ubuntu Linux Pros

  • Easy to learn and use
  • Great support from the community
  • Quick to install and set up
  • Elegant and stylish design
  • Modern and user-friendly interface

Ubuntu Linux Cons

  • Ubuntu Linux has higher operating system requirements

Elementary OS

If you are a macOS user, then the Elementary OS Linux distro will be familiar. The developers try to create a global design that can make every element on the desktop feel and look similar for macOS users.


The Elementary OS desktop apps are launchable from the Dock or Applications menu. Power, network, notifications, and sound options are in the top bar, also known as the Wingpanel.
The AppCenter allows you to install essential applications to get your tasks done. Overall, Elementary OS is a great Linux distro for beginners and is simple to use.

Elementary OS Pros

  • Perfect hardware recognition
  • Minimalist interface resembling macOS
  • Simple to use
  • Ubuntu Foundation

Elementary OS Cons

  • A limited number of installed applications

Zorin OS

If you are a fan of Windows, the Zorin OS would be a great Linux distro for you. It comes with a familiar desktop interface that is gorgeous and simple to navigate. You can also switch to other interfaces to meet your tastes. These include GNOME3, Window XP, and Window 7.
Zorin OS is the only distro in this list designed with Windows users in mind. It includes Wine, a compatibility layer which makes it possible to install Windows apps on Linux. The distribution also integrates PlayOnLinux, a graphical app store to set up many Windows applications.

ZORIN OS Pros

  • Ideal for Windows users
  • An excellent collection of installed applications
  • Modern and elegant interface
  • You can change the interface to suit your preferences

ZORIN OS Cons

  • It takes time to learn

Linux Mint

Linux Mint is another Linux distro based on Ubuntu. Linux Mint offers 3 choices of desktops: Xfce, Mate, and Cinnamon. Each option has its pros and cons, but the Cinnamon is probably the best one for beginners.


This distro integrates familiar components on the desktop such as system tray, start button, or clickable icons. That’s why Linux Mint is an excellent option for those who are new to Linux.
Also, the Linux Mint is very lightweight as it only runs on 9 GB space of hard disk and 512 MB RAM. The lightweight footprint means you could load it up on an older PC and test before setting up on newer hardware.

Linux Mint Pros

  • Require low hardware
  • Great collection of default applications
  • Simple and user-friendly interface
  • Ubuntu Foundation

Linux Mint Cons

  • The interface is a bit old-fashioned

Ubuntu Budgie

Ubuntu Budgie is a gorgeous and straightforward Linux distro for beginners. Ubuntu Budgie has many new features on its Budgie desktop, such as the main menu, a dock, and a panel which includes notifications and some extras. Also, there are many other pre-installed apps to meet your needs, including LibreOffice, web browser Chromium, movie player GNOME MPV, webcam booth, and email.


Also, Ubuntu Budgie comes with a night light choice for those who often do plenty of work during the night and need to reduce the brightness. Ubuntu Budgie simplicity and beauty makes an impression.

Ubuntu Budgie Pros

  • Simple to learn
  • Ubuntu Foundation
  • The interface is gorgeous
  • Many default applications

Ubuntu Budgie Cons

  • Support could be unreliable

Conclusion

There are several things you should know about Linux distros:

  • You can download all of these distributions for free as .iso image files.
  • These distributions can be operated very well on most standard PC hardware, either laptops or desktops.
  • You need to burn ISO images to either a USB flash drive or CD/DVD.
  • It is possible to run all of these Linux distros as “live” instances, which means that you could boot your operating system from the flash drive or CD/DVD and run directly from the RAM of your PC without setting up anything.

Related References