pl_sql.ppt

• PL/SQL is a combination of SQL along
with the procedural features of
programming languages. It was developed
by Oracle Corporation in the early 90's to
enhance the capabilities of SQL. PL/SQL
is one of three key programming
languages embedded in the Oracle
Database, along with SQL itself and Java.
This tutorial will give you great
understanding on PL/SQL to proceed with
Oracle database and other advanced
RDBMS concepts.

• PL/SQL is not a standalone programming
language; it is a tool within the Oracle
programming environment. SQL* Plus is
an interactive tool that allows you to type
SQL and PL/SQL statements at the
command prompt. These commands are
then sent to the database for processing.
Once the statements are processed, the
results are sent back and displayed on
screen.

• To run PL/SQL programs, you should
have the Oracle RDBMS Server installed
in your machine. This will take care of the
execution of the SQL commands. The
most recent version of Oracle RDBMS is
11g. You can download a trial version of
Oracle 11g from the following link −
• Download Oracle 11g Express Edition

• In this chapter, we will discuss the Basic
Syntax of PL/SQL which is a block-
structured language; this means that the
PL/SQL programs are divided and written
in logical blocks of code. Each block
consists of three sub-parts −

S.No Sections & Description
1
Declarations
This section starts with the
keyword DECLARE. It is
an optional section and
defines all variables,
cursors, subprograms, and
other elements to be used
in the program.
2
Executable Commands
This section is enclosed
between the
keywords BEGIN and END
and it is a mandatory
section. It consists of the
executable PL/SQL
statements of the program.
It should have at least one
executable line of code,
which may be just a NULL
command to indicate that
nothing should be
executed.
3
Exception Handling
This section starts with the
keyword EXCEPTION.
This optional section
contains exception(s) that
handle errors in the
program.

• Every PL/SQL statement ends with a
semicolon (;). PL/SQL blocks can be
nested within other PL/SQL blocks
using BEGIN and END. Following is the
basic structure of a PL/SQL block −

• DECLARE <declarations section> BEGIN
<executable command(s)> EXCEPTION
<exception handling> END;

Introduction to PL/SQL
• Procedural Language extension for SQL
• Oracle Proprietary
• 3GL Capabilities
• Integration of SQL
• Portable within Oracle data bases
• Callable from any client

Structure of PL/SQL
• PL/SQL is Block Structured
A block is the basic unit from which all PL/SQL
programs are built. A block can be named
(functions and procedures) or anonymous
• Sections of block
1- Header Section
2- Declaration Section
3- Executable Section
4- Exception Section

Structure of PL/SQL
HEADER
Type and Name of block
DECLARE
Variables; Constants; Cursors;
BEGIN
PL/SQL and SQL Statements
EXCEPTION
Exception handlers
END;

Structure of PL/SQL
DECLARE
a number;
text1 varchar2(20);
text2 varchar2(20) := “HI”;
BEGIN
---------- ---------- ----------
END;
Important Data Types in PL/SQL include
NUMBER, INTEGER, CHAR, VARCHAR2, DATE
etc
to_date(‘02-05-2007','dd-mm-yyyy') { Converts
String to Date}

Structure of PL/SQL
• Data Types for specific columns
Variable_name Table_name.Column_name%type;
This syntax defines a variable of the type of the
referenced column on the referenced table

PL/SQL Control Structure
• PL/SQL has a number of control structures
which includes:
• Conditional controls
• Iterative or loop controls.
• Exception or error controls
• It is these controls, used singly or together, that
allow the PL/SQL developer to direct the flow of
execution through the program.

• Conditional Controls
IF....THEN....END IF;
IF....THEN...ELSE....END IF;
IF....THEN...ELSIF....THEN....ELSE....END IF;

• LOOP
...SQL Statements...
EXIT;
END LOOP;
• WHILE loops
• WHILE condition LOOP
...SQL Statements...
END LOOP;
• FOR loops
• FOR <variable(numeric)> IN [REVERSE]
<lowerbound>..<upperbound> LOOP .... ..... END LOOP;

• Cursor
DECLARE
name varchar2(20);
Cursor c1 is
select t.name
from table t
where date is not null;
BEGIN
OPEN c1;
LOOP
FETCH c1 into name;
exit when c1%NOTFOUND;
END LOOP;
CLOSE c1;
END;

Debuging
• show error
• DBMS_OUTPUT.PUT_LINE(‘ .. ‘);

Execution
• How to execute a function in PL/SQL?
Var issue_flag number;
exec :issue_flag:=fun_name(arg1,arg2,. . . .);
PRINT :issue_flag;
• How to execute a procedure in PL/SQL?
Exec procedure_name(arg1,arg2,. . . .);

References
[1] http://www.csee.umbc.edu/help/oracle8/server.815/a67842/01_oview.htm#740
[2] http://en.wikipedia.org/wiki/PL/SQL
[3] http://www.skillbuilders.com/Tutorials-V2/ora9i_Intro_to_PLSQL/ora9i_Intro_to_PLSQL.cfm

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