10. PL SQL - I

8/2/2019 10. PL SQL - I

http://slidepdf.com/reader/full/10-pl-sql-i 1/22

8/2/2019 10. PL SQL - I


PL/SQL-1 2

CMC

Objectives

• Write your own PL/SQL code using conditional

statements and loop constructs

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PL/SQL-1 3

CMC

Introduction

• SQL does not have any procedural capabilities such as

looping and branching nor does it have any conditional

checking capabilities vital for data testing before

storage.

• PL/SQL adds to the power of SQL and provides the

user with all the facilities of a programming

environment.

• PL/SQL bridges the gap between database technology

and procedural programming languages.

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PL/SQL-1 4

CMC

• Via PL/SQL you can insert, delete, update and retrieve

table data as well as use procedural techniques such aswriting loops or branching to another block of code.

• PL/SQL is really an extension of SQL.

• PL/SQL blocks can contain any number of SQL

statements. It allows you to logically group a number of

SQL statements and pass them to the DBA as a single

block.

• Without PL/SQL, DBA has to process SQL statements

one at a time.

Introduction contd..

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PL/SQL-1 5

CMC

PL/SQL Block

• A standard PL/SQL code segment is called a block. Astandard PL/SQL block is made up of three sections.

1. Declaration Section is meant for declaring variables

and constants.

2. Executable Statements Section is meant for

manipulating objects during execution.

3. Exception Handling Section - any errors or

exceptions raised during execution of the PL/SQL

block are handled here.

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PL/SQL-1 6

CMC

PL/SQL Engine

• The PL/SQL Engine accepts the procedural requests

and database queries from the PL/SQL code block andtransfers them to the Procedural Statement Executer

and the SQL Statement Executer respectively.

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PL/SQL-1 7CMC

Advantages of PL/SQL

• Procedural Capabilities: Offers constructs for

conditional selection, iteration etc. Variable and

constant declarations are possible.

• Improved Performance: Processing is fast since entireblock is sent to RDBMS rather than one statement at a

time.

• Enhanced Productivity: PL/SQL can be embedded inORACLE application development tools and 3 GL

interface program.

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PL/SQL-1 8CMC

• Portability: An application developed in PL/SQL is

portable across h/w and o.s. platforms.

• Integration with RDBMS: Variables in PL/SQL can

belong to any SQL datatype such as - CHAR, DATE

etc.

Advantages of PL/SQL contd..

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PL/SQL-1 9CMC

Variables and Constants

• A PL/SQL variable can be used either in SQL or

PL/SQL statements provided it is declared beforereferencing it.

Data Types:

• BINARY_INTEGER Type: You use the

BINARY_INTEGER datatype to store signed integers.

Variables

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PL/SQL-1 10CMC

• NUMBER Type: You use the NUMBER datatype to

store fixed or floating point numbers of virtually any size.

• CHAR Type: You use the CHAR datatype to store

fixed-length character data.

• VARCHAR2 Type: You use the VARCHAR2 datatype

to store variable-length character data.

• LONG Type: You use the LONG datatype to store

variable-length character strings.

Variables contd..

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PL/SQL-1 11CMC

• RAW Type: You use the RAW datatype to store binary

data or byte strings.

• LONG RAW Type: You use the LONG RAW datatype

to store binary data or byte strings.

• BOOLEAN Type: You use the BOOLEAN datatype to

store the values TRUE and FALSE and the non-value

NULL.

• DATE Type: You use the DATE datatype to store fixed-length date values. The DATE datatype takes no

parameters.

Variables contd..

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PL/SQL-1 12CMC

• ROWID Type: Each row in the database has an

address of the type Data Object Number.Relative File

Number.Block Number.Slot Number

• MLSLABEL Type: With Trusted Oracle, you use the

MLSLABEL datatype to store variable- length, binary

operating system labels. Trusted Oracle uses labels to

control access to data.

Variables contd..

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PL/SQL-1 13CMC

Constants

• Declaration of a constant is similar to the declaration of a variable except that the keyword CONSTANT must be

added and a value must be assigned.

Variables and Constants contd..

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PL/SQL-1 14CMC

Declaration Using Attributes

• This attribute provides the data type of a variable,

constant or column.

• %TYPE attribute is useful while declaring a variable that

has same data type as a table column.

%TYPE attribute

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PL/SQL-1 15CMC

%ROWTYPE attribute

• This attribute is used to declare a variable to be a

record having the same structure as a row in a table.

• The row is represented as a record and its fields have

the same names and data types as the columns in the

table or view.

Declaration Using Attributes contd..

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PL/SQL-1 16CMC

Operators

Logical:

• AND• OR• NOT

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PL/SQL-1 17CMC

Conditional Control

if (condition) then if (condition) then

statements statements

else elsif (condition) thenstatements statements

end if; else

statements

end if;

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PL/SQL-1 18CMC

Iterative Control

1. Endless Loop

LOOPstatements

..........

END LOOP;

LOOP and END LOOP are the keywords.

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PL/SQL-1 19CMC

Iterative Control contd..

2. For Loop

FOR i IN 1..10

LOOP

statements.........

END LOOP;

- FOR loop index is implicitly declared to be of datatype NUMBER.

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PL/SQL-1 20CMC

Iterative Control contd..

3. While Loop

WHILE (condition)

LOOP

.........

statements

.........

END LOOP;

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PL/SQL-1 21CMC

GOTO Statement• The GOTO statement changes the flow of control

within the PL/SQL block.

• GOTO statement is used in combination with label-

names.

• Labels are used as markers before the block or

executable statements to which control is to betransferred.

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10. PL SQL - I