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Database Programming (CS 423)
Course Coordinator:
Dr. Irshad Ahmed Abbasi
Email: aabasy@ub.edu.sa
www.ub.edu.sa ‫المعلومات‬ ‫وتقنية‬ ‫الحاسبات‬ ‫كلية‬

Definition :-
PL/SQL, the Oracle procedural extension of SQL, is a portable,
high-performance transaction-processing language.
Introduction
‫المعلومات‬ ‫وتقنية‬ ‫الحاسبات‬ ‫كلية‬

Main Features of PL/SQL
PL/SQL combines the data-manipulating power of SQL with
the processing power of procedural languages.
When you can solve a problem with SQL, you can issue SQL
statements from your PL/SQL program, without learning
new APIs.
Like other procedural programming languages, PL/SQL lets
you declare constants and variables, control program flow,
define subprograms, and trap runtime errors.
You can break complex problems into easily understandable
subprograms, which you can reuse in multiple applications.

Types of SQL : static and dynamic SQL.
Static SQL is SQL whose full text is known at
compilation time.
Dynamic SQL is SQL whose full text is not known
until run time.
Dynamic SQL lets you make your applications
more flexible and versatile.
Types of SQL

PL/SQL Diagram

Advantages of PL/SQL
PL/SQL has these advantages:
1. Tight Integration with SQL
2. High Performance
3. High Productivity
4. Portability
5. Scalability
6. Manageability
7. Support for Object-Oriented Programming
8. Support for Developing Web Applications
9. Support for Developing Server Pages

Error Handling
PL/SQL makes it easy to detect and handle errors. When an
error occurs, PL/SQL raises an exception. Normal execution
stops and control transfers to the exception-handling part of the
PL/SQL block. You do not have to check every operation to
ensure that it succeeded, as in a C ++ program.

The basic unit of a PL/SQL source program is the block,
which groups related declarations and statements.
A PL/SQL block is defined by the keywords DECLARE, BEGIN,
EXCEPTION, and END.
Blocks contain :-
 Declarative part
 An executable part (is require)
 Exception-handling part.
 Block Label.
Declarations are local to the block and cease to exist when the block
completes execution, helping to avoid cluttered namespaces for
variables and subprograms.
Blocks can be nested: Because a block is an executable statement, it can
appear in another block wherever an executable statement is allowed.
Blocks

Example
<< label >> (optional)
DECLARE -- Declarative part (optional)
-- Declarations of local types, variables, & subprograms
BEGIN -- Executable part (required)
-- Statements (which can use items declared in declarative part)
[EXCEPTION -- Exception-handling part (optional)
-- Exception handlers for exceptions (errors) raised in executable part]
END;

Variables and Constants
PL/SQL lets you declare variables and constants, and then use
them wherever you can use an expression. As the program runs,
the values of variables can change, but the values of constants
does not.

Subprograms
A PL/SQL subprogram is a named PL/SQL block that can be invoked
repeatedly.If the subprogram has parameters, their values can differ
for each invocation.
PL/SQL has two types of subprograms, procedures and functions.
A function returns a result.

Packages
package is a schema object that groups logically related PL/SQL
types, variables, constants, subprograms, cursors, and
exceptions. A package is compiled and stored in the database,
where many applications can share its contents. You can think of
a package as an application.

Input and Output
‫اﻟﻤﻌﻠﻮﻣﺎت‬ ‫ﺗﻘﻨﯿﺔ‬ ‫و‬
‫ت‬ ‫اﻟﺤﺎﺳﺒﺎ‬ ‫ﻛﻠﯿﺔ‬
Most PL/SQL input and output (I/O) is done with SQL
statements that store data in database tables or query those
tables.

Data Abstraction
Data abstraction lets you work with the essential properties of
data without being too involved with details. You can design a data
structure first, and then design algorithms that manipulate it.
1 Cursors
2 Composite Variables
3 %ROWTYPE Attribute
4 %TYPE Attribute
Abstract Data Types

Cursors
A cursor is a pointer to a private SQL area that stores
information about processing a specific SQL statement or
PL/SQL SELECT INTO statement. You can use the cursor to
retrieve the rows of the result set one at a time. You can use
cursor attributes to get information about the state of the
cursor—for example, how many rows the statement has
affected so far. For more information about cursors,

Composite Variables
A composite variable has internal components, which you can
access individually. You can pass entire composite variables to
subprograms as parameters. PL/SQL has two kinds of composite
variables, collections and records.
In a collection, the internal components are always of the same
data type, and are called elements. You access each element by
its unique index. Lists and arrays are classic examples of
collections.
In a record, the internal components can be of different data
types, and are called fields. You access each field by its name. A
record variable can hold a table row, or some columns from a
table row.

%ROWTYPE Attribute
The %ROWTYPE attribute lets you declare a record that
represents either a full or partial row of a database table or
view. For every column of the full or partial row, the record has
a field with the same name and data type. If the structure of the
row changes, then the structure of the record changes
accordingly.

%TYPE Attribute
The %TYPE attribute lets you declare a data item of the same data type
as a previously declared variable or column (without knowing what that
type is). If the declaration of the referenced item changes, then the
declaration of the referencing item changes accordingly.
The %TYPE attribute is particularly useful when declaring variables to
hold database values.

Abstract Data Types
An Abstract Data Type (ADT) consists of a data structure and
subprograms that manipulate the data. The variables that form the
data structure are called attributes. The subprograms that
manipulate the attributes are called methods.
ADTs are stored in the database. Instances of ADTs can be stored in
tables and used as PL/SQL variables.
ADTs let you reduce complexity by separating a large system into
logical components, which you can reuse.
In the static data dictionary view *_OBJECTS, the OBJECT_TYPE of an
ADT is TYPE. In the static data dictionary view *_TYPES,
the TYPECODE of an ADT is OBJECT.

Control Statements
PL/SQL has three categories of control statements:
Conditional selection statements, which let you run different
statements for different data values.
Loop statements, which let you repeat the same statements with a
series of different data values.
Sequential control statements, which allow you to go to a
specified, labelled statement, or to do nothing.

A PL/SQL unit is one of these:
•PL/SQL anonymous block
•FUNCTION
•LIBRARY
•PACKAGE
•PACKAGE BODY
•PROCEDURE
•TRIGGER
•TYPE
PL/SQL Units and Compilation Parameters

Blocks in PL SQL
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.
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.
Exception Handling
This section starts with the keyword EXCEPTION. This optional
section contains exception(s) that handle errors in the program.

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

DECLARE
message varchar2(20):= 'Hello, World!';
BEGIN
dbms_output.put_line(message);
END;
/
Before this We have to set the serveroutput to on

BEGIN
FOR someone IN (
SELECT * FROM employees
WHERE employee_id < 120
ORDER BY employee_id )
LOOP DBMS_OUTPUT.PUT_LINE('First name = ' ||
someone.first_name || ', Last name = ' || someone.last_name);
END LOOP;
END; /

The end; line signals the end of the PL/SQL block.
To run the code from the SQL command line, you may need to
type / at the beginning of the first blank line after the last line of
the code.
When the above code is executed at the SQL prompt, it
produces the following result.
Hello World PL/SQL procedure successfully
completed.

PL/SQL Identifiers
The PL/SQL Identifiers
PL/SQL identifiers are constants, variables, exceptions,
procedures, cursors, and reserved words.
The identifiers consist of a letter optionally followed by more
letters, numerals, dollar signs, underscores, and number signs
and should not exceed 30 characters.
By default, identifiers are not case-sensitive.
So you can use integer or INTEGER to represent a numeric
value.
You cannot use a reserved keyword as an identifier.

The PL/SQL Delimiters

Delimiter Description
+, -, *, / Addition, subtraction/negation, multiplication, division
% Attribute indicator
' Characterstring delimiter
. Component selector
(,) Expression or list delimiter
: Host variable indicator
, Item separator
" Quoted identifier delimiter
= Relational operator
@ Remote access indicator
; Statementterminator
:= Assignment operator
=> Association operator
|| Concatenation operator
** Exponentiation operator
<<, >> Label delimiter (begin and end)
/*, */ Multi-line comment delimiter (begin and end)
-- Single-line comment indicator
.. Range operator
<, >, <=, >= Relational operators
<>, '=, ~=, ^= Different versions of NOT EQUAL

Program comments are explanatory statements that can be included in the
PL/SQL code that you write and helps anyone reading its source code.
All programming languages allow some form of comments.
The PL/SQL supports single-line and multi-line comments.
All characters available inside any comment are ignored by the PL/SQL
compiler.
The PL/SQL single-line comments start with the delimiter -- (double hyphen)
and
multi-line comments are enclosed by /* and */.
DECLARE
-- variable declaration
message varchar2(20):= 'Hello, World!';
BEGIN /* * PL/SQL executable statement(s) */
dbms_output.put_line(message);
END; /
The PL/SQL Comments

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