Home > Differences > What is SQL, PL/SQL, T-SQL and difference between them

What is SQL, PL/SQL, T-SQL and difference between them

Today I got an email from a student who is pursuing his Bachelors degree in Computer Application (BCA). He visited my blog and sent me an email regarding his confusion with terms like SQL, T-SQL, PL/SQL, and asked me what is differences between them and how are they related? I had a chat with him and told the basic differences, but he further asked me how they are related to Microsoft SQL Server, Oracle, MySQL, etc? As he is studying SQL only based upon Oracle in his course curriculum, these all terms were not clear to him, so I cleared all his doubts while chatting with him.

After a while I had a same reminiscence that when I was a student I also had these doubts and confusions, and there was nobody to guide me, but I gradually came to know about this and it took some time. Thus, I’am taking this opportunity to put all these things together here in a single blog post for my readers (specially students) and for my reference as well.

–> SQL: stands for Structured Query Language and is pronounced as Sequel, and in early days it was also known as SEQUEL only.

– IBM in early 1970s developed SEQUEL which stands for Structured English QUEry Langauge for their RDBMS. The acronym was later changed to SQL, as SEQUEL was already trademarked by some UK based aircraft company.

–> PL/SQL: stands for Procedural Language/Structured Query Language and is used with Oracle database to create PL/SQL units such as Procedures, Functions, Packages, Types, Triggers, etc. which are stored in the database for reuse by applications that use any of the Oracle Database programmatic interfaces.

– Oracle in 1970s known as “Relational Software” saw SQL potential and influenced by Boyce, Codd and Chamberlin developed their own RDBMS product which was commercially available as Oracle Database. Oracle is supported on many Operating Systems like Windows, Linux, Solaris, AIX, OpenVMS, etc. [Oracle Database]

–> DB2: IBM during early 1980s made SQL commercially available with its product known as IBM DB2 from its prototype “System R”. [IBM DB2]

–> SQL Standardization: Later in 1986 SQL was adopted as a Standard by ANSI (American National Standards Institute) as SQL-86, and today the latest Standard is known as SQL:2011

✔ As a standarg SQL should support following:

– Language elements: Clauses, Expressions, Predicates, Queries, Statements.
– Operators: =, , >, =, <=, BETWEEN, LIKE, IN, NOT IN, IS, IS NOT, AS, etc.
– Conditional expressions: CASE, IF ELSE
– Queries: which include SELECT, FROM, WHERE, GROUP BY, HAVING, ORDER BY, etc.
– Data Types: Numeric, Char, Bit, Date and Time
– NULL or 3VL (Three value Logic)

–> T-SQL: stands for Transact-SQL, and is Sybase & Microsoft’s proprietary extension. T-SQL is very similar to PL/SQL, one can create T-SQL units such as Procedures, Functions, Types, Triggers, etc. as mentioned above.

– In 1987 Sybase shipped their first RDBMS product known as Sybase SQL Server. [Sybase]

– In 1988-89 Microsoft had an agreement with Sybase and ported the Sybase RDBMS to OS/2 platform and marketed it as Microsoft SQL Server 1.0, which was equivalent to Sybase SQL Server 3.0. [Microsoft SQL Server]

– In 1993 Sybase and Microsoft dissolved their partnership, and Microsoft bought the SQL Server code base from Sybase and both went different streams to develop their own product.

– Till SQL Server 2000 Microsoft has Sybase code base, and this was completely written in SQL Server 2005.

– Microsoft SQL Server is only supported on Windows Operating Systems.

–> MySQL: was founded by a Swedish Company MySQL AB in 1995 and is the most widely used open-source RDBMS. The MySQL development project has made its source code available under the terms of the GNU General Public License. MySQL does not currently comply with the full SQL standard. In 2008 Oracle corporation completely acquired MySQL. MySQL is supported on many Operating Systems like Windows, Linux, Solaris, OS X and FreeBSD. []

–> FoxPRO and dBase: were very popular DataBase Management System (DBMS) products in mid 1980s and 1990s. They lack some RDBMS features and are out of support now, but are still being used in various legacy systems.

– FoxPRO is supported by Microsoft and was a text-based Procedural programming language and DBMS, for MD DOS, Windows, and UNIX. Microsoft Visual FoxPRO 9.0 being the latest and probably the last version published in 2007. [FoxPRO msdn]

– dBase was a very popular DBMS package including core Database engine, a Query system, a Forms engine and a xBase programming language with *.dbf file format. []

–> Here is a complete timeline that shows SQL and how it got evolved as different Products by different Vendors/Companies (click on the image to expand):


–> There are many other popular SQL Products/System softwares available in market, and major of them are:
1. Oracle database
2. Microsoft SQL Server
3. IBM DB2
4. MySQL
5. PostgreSQL
6. Teradata


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  1. Abhinaya
    July 8, 2017 at 11:19 am

    Thanku sir..for the nice explanation.Actually iam going to attend an interview in oracle.could you mind suggesting me a few topics that i should know before attending it?

  2. Faye
    March 4, 2017 at 5:53 am

    That’s very clear. I have a question though. For plsql that’s written to run against an Oracle database, will the same script work on Microsoft SQL Server?

  3. Blake
    June 18, 2016 at 6:56 pm

    Hi thank you for this explanation.
    I have a question to ask you.
    I am new to the topic and I was thinking about buying a book that he knew explain SQL and MySQL databases.
    If you was teaching, for example at the University, which book would you recommend to start whit it’s?

  4. Manzoor Ahmed
    May 6, 2016 at 12:14 pm

    Giving a big picture is always helpfull!
    The blog is Very helpfull… as it explains how it started and how transformed to the present form… 🙂

  5. December 12, 2015 at 6:11 pm

    Nice Explain sir,


  6. prasad
    November 6, 2015 at 9:14 pm

    i am good at java programming,
    i want to learn sql.
    is it proper?

  7. May 5, 2015 at 4:36 pm

    Reblogged this on Christopher J. McClellan and commented:
    A brief history of SQL.

    • May 5, 2015 at 4:50 pm

      Thanks for re-blogging.

      Can you please also rate the post at the top?


  1. January 2, 2017 at 5:39 pm
  2. April 30, 2016 at 3:08 pm
  3. June 7, 2015 at 8:22 pm

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