PL/SQL is Oracle's Procedural Language extension to SQL. PL/SQL's language syntax, structure and datatypes are similar to that of ADA. The language includes object oriented programming techniques such as encapsulation, function overloading, information hiding (all but inheritance), and so, brings state-of-the-art programming to the Oracle database server and a variety of Oracle tools.
Need for PL/SQL
SQL statements are defined in term of constraints we wish to fix on the result of a query. Such a language is commonly referred to as declarative. This contrasts with the so called procedural languages where a program specifies a list of operations to be performed sequentially to achieve the desired result. PL/SQL adds selective (i.e. if...then...else...) and iterative constructs (i.e. loops) to SQL.
PL/SQL is most useful to write triggers and stored procedures. Stored procedures are units of procedural code stored in a compiled form within the database.
PL/SQL programs are organised in functions, procedures and packages (somewhat similar to Java packages). There is a limited support for object-oriented programming. PL/SQL is based on the Ada programming language, and as such it shares many elements of its syntax with Pascal.
