This question already has an answer here:

I am very new to the databases just have basic knowledge about it.

I want to learn sql language and dont know where to start. Please help me to start with it. And what is the difference between sql and PostgreSQL? What are the different languages to maintain databases.

Any help will be appreciated.

marked as duplicate by ypercubeᵀᴹ, Philᵀᴹ, Kenneth Fisher, Kin Shah, Max Vernon Feb 15 '14 at 22:08

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.


SQL is a declarative data query language. PostgreSQL is a database which supports SQL (as do all RDBMS's). Oracle supports SQL, so does MySQL &c. There are differences - PostgreSQL is very ANSI compliant, whereas Oracle and MySQL not so much.

If you want to learn, Google SQL tutorials and maybe use dbfiddle.uk (more servers) or db-fiddle.com (a bit easier) to test - or just download PostgreSQL/MySQL/Firebird. The three of these are Open Source and free to use for any purpose, bar MySQL: you can't distribute a closed-source application using MySQL without paying a licence fee to Oracle because of the dual GPL/commercial licencing.

From here:

  • MySQL Commercial License for OEMs, ISVs and VARs Oracle provides its MySQL database server and MySQL Client Libraries under a dual license model designed to meet the development and distribution needs of both commercial distributors (such as OEMs, ISVs and VARs) and open source projects.

What this means is that basically, if you want to distribute MySQL based apps without paying a fee, your app must be under the GPL version 2.

You can also download Oracle XE for free (latest version as of 05/2018) is still 11g - limitations from here:

  • Oracle Database XE can be installed on any size host machine with any number of CPUs (one database per machine), but XE will store up to 11GB of user data, use up to 1GB of memory, and use one CPU on the host machine.

There's also:

Microsoft SQL Server Express with limitations 1GB RAM and 10GB data - from here and here.

Your question is very general (too broad) for this forum - you need to read a couple of books/tutorials and come back with specific questions (with what you've tried - use one of the fiddles above for your DDL for your sample data (CREATE TABLE...), DML (INSERT INTO blah VALUES (...);) in your questions.

  • There is also SQL-Server Express. – ypercubeᵀᴹ Feb 16 '14 at 0:41
  • 1
    "free to use for any purpose" is not true for MySQL because of it's GPL license: you are not free to distribute it with your non-GPL application and it's not free if you create a derivative work based on it. – a_horse_with_no_name Feb 16 '14 at 12:09
  • Thanks for the heads-up! FInally got round to updating the post - I'm doing a bit of spring-cleaning of my old (newbie) posts <cringe...(sometimes!)> – Vérace May 21 '18 at 10:54

Not the answer you're looking for? Browse other questions tagged or ask your own question.