Question: I want to clarify difference between sequel vs SQL? Any one here know the difference between them?

Answer: 
They are the same.

From [Wikipedia](http://en.wikipedia.org/wiki/SQL): 

> 
> **SQL** (/ˈɛs kjuː ˈɛl/ "S-Q-L"[4]; Structured Query Language[5][6][7][8])
>  is a special-purpose programming language designed for managing data
>  held in a relational database management system (RDBMS).
> 
> 
> 

Some people pronounce it "S-Q-L", while others pronounce it "sequel".

For more on the pronunciation of this term: 

**<https://english.stackexchange.com/questions/7231/how-is-sql-pronounced>**

<http://patorjk.com/blog/2012/01/26/pronouncing-sql-s-q-l-or-sequel/>
I spent some time researching this old issue because it has come up *again* at my company. As John Woo said, it's a matter of *pronunciation*, not spelling. SQL is pronounced "sequel" by many, and there is some history there, beyond just trying to make an acronym out of an initialism. (NASA is an acronym; IBM is an initialism). 

But in writing, the best and most consistent way to refer to SQL Server or SQL databases, etc. is "SQL" --which takes the article "an" based on the initial letter "S". IBM and Microsoft style guides both agree on "an SQL " in writing, even if it might be pronounced "sequel" in some contexts. 

Our company was confused on this point for some years because a Google search shows much greater use of "...a SQL " in *English* hits. Also we have long relied on the Microsoft Manual of Style, and their "rule" was easily misinterpreted. They've updated it for the 4th edition--see pp 387-388. SO: In conversation, do what you want, as long as you understand that "sequel" works in English chat, but not necessarily for people whose native language is not English. **In writing, it's S-Q-L, and the article is "an".**