There are so many variants of SQL that it is hard sometimes to figure out what to use. Here is a short article that briefly explains the difference between SQL and PL/SQL. Enjoy!

What is SQL?

SQL (pronounced “sequal”) stands for Structured Query Language. Withe SQL, you can view data – called Data Definiton Language or DDL and manipulate data – called Data Manipulation Languate or DML. All of the above are just a fancy way to say that with SQL, the user can both view and alter records in the database. To help , here are a couple of queries:

DDL or View

SELECT * FROM employees

View all of the records in the employee table

DML or Manipulate

UPDATE employees SET employeefirstname = ‘John’ WHERE employeeid = 101

Find the record for employee ID 101 and change the first name to John

What is PL/SQL?

The official answer is from the PL/SQL User Guide:
PL/SQL, Oracle’s procedural extension of SQL, is an advanced fourth-generation programming language (4GL). It offers software-engineering features such as data encapsulation, overloading, collection types, exceptions, and information hiding. PL/SQL also supports rapid prototyping and development through tight integration with SQL and the Oracle database.
Huh? That is what I thought at the beginning. But at a high level, all this means is that it can do all of the things that regular SQL can do, but also, it is procedural and can be used like a programming language (C++, Java, etc.) For instance, you can use loops and If . . . Then statements in your PL/SQL statements (Programs).

Here is a definition of PL/SQL from Lewis Cunningham (an Oracle database expert):

“If I wanted to create my own, very short, definition of PL/SQL it would be this: PL/SQL is the Oracle native programming language that provides database-centric application development. It can natively call static SQL and provides multiple methods of calling dynamic SQL.

Mr. Cunningham also does a very good job of spelling out the differences between SQL and PL/SQL.

SQL is a data oriented language for selecting and manipulating sets of data. PL/SQL is a procedural language to create applications. You don’t normally have a “SQL application”. You normally have an application that uses SQL and a relational database on the back-end. PL/SQL can be the application language just like Java or PHP can. SQL may be the source of data for your screens, web pages and reports. PL/SQL might be the language you use to build, format and display those screens, web pages and reports.

Think of it like this: The code that makes your program function is PL/SQL. The code that manipulates the data is SQL DML. The code that creates stored database objects is SQL DDL. DDL compiles the code that is written in PL/SQL. PL/SQL may call SQL to perform data manipulation. The commands that format the output of a tool are not related to the SQL standard or to PL/SQL.
To muddy the waters a little more, while you cannot write an application in SQL, you can use a procedural language to automate parts. These are called Stored Procedures and here is a link to all you want to know about stored procedures on this site.