PL / SQL

Faisal Anwer & Mohammad Nadeem

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DISADVANTAGES OF SQL

SQL does not have any procedural capabilities:

Condition checking

Looping and branching

There is no provision for exception handling.

To overcome these problems and provide some additional

benefits, PL/SQL was developed.

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PL/SQL

PL/SQL is a programming language that supports SQL

data manipulation. But also provides:

facilities of conditional checking, looping and

branching.

provides exception handing facility.

supports variables to handle intermediate results.

and much more.

It is a superset of SQL.

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PL/SQL GENERIC BLOCK

PL/SQL blocks contain three sections

Declare section

Executable section

Exception-handling section

The executable section is the only mandatory section of the

block.

Both, the declaration and exception-handling sections are

optional.

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PL/SQL GENERIC BLOCK

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VARIOUS SECTIONS

Declare Section:

Variables and objects can be declared and initialized (if required) in

this section.

Once declared, they can be used in SQL statements.

Begin Section:

It consists of a set of SQL and PL/SQL statements.

Data manipulation, retrieval, looping and branching constructs are

specified in this section.

Exception Section:

Handles the errors that arise during execution on PL/SQL

statements.

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EXAMPLE

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INPUT / OUTPUT IN PL/SQL

Input:

n1 := &n1; (for command line inputting)

n1 := :n1; (for GUI inputting)

Output:

dbms_output.put_line(‘Your message');

dbms_output.put_line(‘ ‘) displays a message string.

If the Output is OFF and it can be made ON by:

SET SERVEROUTPUT ON;

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EXAMPLE

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EXAMPLE

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BASIC DATA TYPES

Number(p,s)

Char(n)

Varchar2(n)

Date

Boolean

%Type:

Declares a variable to have the same data type as that

of a previously defined variable or of a column in a

table.

Ex- Cname Client_Master.Name%Type;

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LOGICAL COMPARISONS

>

<

=

<=

>=

<>

Logical operators:

AND

OR

NOT

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CONDITIONAL STATEMENT

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EXAMPLE F

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LOOPING

Loop:

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EXAMPLE

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LOOPING

While loop:

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EXAMPLE

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LOOPING

For loop:

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EXAMPLE

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WHAT WE SAW TODAY

Generic PL/SQL Block

Various sections of a PL/SQL Block

Input/Output

Logical operators

Conditional Statement

Looping

Loop

While loop

For loop

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EXAMPLE

Write a PL/SQL code block that will accept an account no

from user and deduct 100 Rs from it if its balance it less

than some minimum balance.

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Write a PL/SQL code block that will accept an account no from user and

deduct 100 Rs from it if its balance it less than some minimum balance.

EXERCISE

Enter a number. If the number is 1 then print ‘One’. If the

number is 2 then print ‘Two’. Else print ‘’Neither One nor

Two’.

Enter an year. Find out whether it is a leap year or not.

Print 10 odd numbers starting from 1.

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