PL/SQL is a block structured language that enables developers to combine the power of SQL with procedural statements

Contents
 What is PL/SQL
 Architecture PL/SQL
 Difference sql/plsql
 Blocks
 Variables
 Hello program

PL/SQL
 PL/SQL is an extension of Structured Query Language (SQL)
that is used in Oracle. Unlike SQL, PL/SQL allows the
programmer to write code in a procedural format.
 Full form of PL/SQL is "Procedural Language extensions to
SQL".
 It combines the data manipulation power of SQL with the
processing power of procedural language to create super
powerful SQL queries.
 PL/SQL means instructing the compiler 'what to do' through
SQL and 'how to do' through its procedural way.
 Similar to other database languages, it gives more control to
the programmers by the use of loops, conditions and object-
oriented concepts.

 Disadvantages of SQL:
 SQL doesn’t provide the programmers with a
technique of condition checking, looping and
branching.
 SQL statements are passed to Oracle engine one at a
time which increases traffic and decreases speed.
 SQL has no facility of error checking during
manipulation of data.

Advantages of Pl/sql
 Block structures
 Procedural language capability
 Better performance
 Error handling

SQL PL/SQL
SQL is a single query that is
used to perform DML and
DDL operations.
PL/SQL is a block of codes
that used to write the entire
program blocks/ procedure/
function, etc.
It is declarative, that defines
what needs to be done,
rather than how things need
to be done.
PL/SQL is procedural that
defines how the things
needs to be done.
Execute as a single
statement.
Execute as a whole block.
Mainly used to manipulate
data.
Mainly used to create an
application.
Cannot contain PL/SQL
code in it.
It is an extension of SQL, so
it can contain SQL inside it.

Architecture of Pl/sql
 The PL/SQL architecture mainly consists of following
three components:
 PL/SQL block
 PL/SQL Engine
 Database Server

PL/SQL block:
 This is the component which has the actual PL/SQL code.
 This consists of different sections to divide the code logically (declarative
section for declaring purpose, execution section for processing statements,
exception handling section for handling errors)
 It also contains the SQL instruction that used to interact with the database
server.
 All the PL/SQL units are treated as PL/SQL blocks, and this is the starting stage
of the architecture which serves as the primary input.
 Following are the different type of PL/SQL units.
 Anonymous Block
 Function
 Library
 Procedure
 Package Body
 Package Specification
 Trigger
 Type
 Type Body

 PL/SQL Engine
 PL/SQL engine is the component where the actual
processing of the codes takes place.
 PL/SQL engine separates PL/SQL units and SQL part
in the input The separated PL/SQL units will be
handled by the PL/SQL engine itself.
 The SQL part will be sent to database server where the
actual interaction with database takes place.
 It can be installed in both database server and in the
application server.

 Database Server:
 This is the most important component of Pl/SQL unit
which stores the data.
 The PL/SQL engine uses the SQL from PL/SQL units
to interact with the database server.
 It consists of SQL executor which parses the input SQL
statements and execute the same.

Plsql block
 Blocks contain both PL/SQL as well as SQL
instruction. All these instruction will be executed as a
whole rather than executing a single instruction at a
time.
 PL/SQL blocks have a pre-defined structure in which
the code is to be grouped. Below are different sections
of PL/SQL blocks.
 Declaration section
 Execution section
 Exception-Handling section

 Declare section starts with DECLARE keyword in which
variables, constants, records as cursors can be declared
which stores data temporarily. It basically consists
definition of PL/SQL identifiers. This part of the code is
optional.
 Execution section starts with BEGIN and ends
with END keyword. This is a mandatory section and here
the program logic is written to perform any task like loops
and conditional statements. It supports
all DML commands, DDL commands and SQL*PLUS
built-in functions as well.
 Exception section starts with EXCEPTION keyword.This
section is optional which contains statements that are
executed when a run-time error occurs. Any exceptions
can be handled in this section.

 Types of PL/SQL block
PL/SQL blocks are of mainly two types.
 Anonymous blocks
 Named Blocks

PL/sql identifiers
 Variables:
Variables in PL/SQL must be declared prior to its use.
They should have a valid name and data type as well.
 Syntax for declaration of variables:
 variable _name datatype [NOT NULL := value ];

Naming rules for PL/SQL variables
 The variable in PL/SQL must follow some naming
rules like other programming languages.
 The variable_name should not exceed 30 characters.
 The name of the variable must begin with ASCII letter.
The PL/SQL is not case sensitive so it could be either
lowercase or uppercase. For example: v_data and
V_DATA refer to the same variables.
 You should make your variable easy to read and
understand, after the first character, it may be any
number, underscore (_) or dollar sign ($).
 NOT NULL is an optional specification on the
variable.

 Declaring and usage of variables in the program

Variable scope
 Global variable
 Local variable
 Example of both local and global variable

Comments
 Commenting code simply instructs the compiler to
ignore that particular code from executing.
 Comment can be used in the program to increase the
readability of the program. In PL/SQL codes can be
commented in two ways.
 Single line comment(---)
 Multiline comment(/*…………………*/)

Constants
 A constant is a value used in a PL/SQL block that remains
unchanged throughout the program.
 It can be declared and used instead of actual values.
 Syntax:
constant_name CONSTANT datatype := VALUE;

LOOP
Syntax: LOOP
Sequence of statements;
END LOOP;

PL/SQL is a block structured language that enables developers to combine the power of SQL with procedural statements

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