PL/SQL notes

PL/SQL Tutoriali

Table of Contents
PL/SQL Tutorial........................................................................iii
Audience..................................................................................iii
Prerequisites ............................................................................iii
Copyright & Disclaimer Notice..................................................iii
PL/SQL Overview..................................................................... 1
Features of PL/SQL ................................................................................... 1
Advantages of PL/SQL .............................................................................. 2
Environment............................................................................. 3
Step 1 ........................................................................................................ 3
Step 2 ........................................................................................................ 4
Step 3 ........................................................................................................ 4
Step 4 ........................................................................................................ 5
Step 5 ........................................................................................................ 6
Step 6 ........................................................................................................ 6
Step 7 ........................................................................................................ 7
Step 8 ........................................................................................................ 7
Step 9 ........................................................................................................ 8
Step 10 ...................................................................................................... 9
Step 11 .................................................................................................... 10
Final Step................................................................................................. 11
Text Editor ............................................................................................... 12
Basic Syntax .......................................................................... 13
The 'Hello World' Example:...................................................................... 13
The PL/SQL Identifiers ............................................................................ 14
The PL/SQL Delimiters ............................................................................ 14
The PL/SQL Comments........................................................................... 15
PL/SQL Program Units ............................................................................ 15
Data Types............................................................................. 17
PL/SQL Scalar Data Types and Subtypes............................................... 17
PL/SQL Numeric Data Types and Subtypes............................................ 18
PL/SQL Character Data Types and Subtypes ......................................... 19
PL/SQL Boolean Data Types................................................................... 19iii
PL/SQL Datetime and Interval Types ...................................................... 19
PL/SQL Large Object (LOB) Data Types................................................. 20
PL/SQL User-Defined Subtypes .............................................................. 21
NULLs in PL/SQL .................................................................................... 21
Variables ................................................................................ 22
Variable Declaration in PL/SQL ............................................................... 22
Initializing Variables in PL/SQL................................................................ 23
Variable Scope in PL/SQL ....................................................................... 23
Assigning SQL Query Results to PL/SQL Variables ................................ 24
Constants............................................................................... 26
Declaring a Constant ............................................................................... 26
The PL/SQL Literals ................................................................................ 27
Operators ............................................................................... 28
Arithmetic Operators................................................................................ 28
Example:.................................................................................................. 29
Relational Operators................................................................................ 29
Example:.................................................................................................. 29
Comparison Operators ............................................................................ 30
LIKE Operator:......................................................................................... 31
BETWEEN Operator:............................................................................... 31
IN and IS NULL Operators:...................................................................... 32
Logical Operators .................................................................................... 33
Example:.................................................................................................. 33
PL/SQL Operator Precedence................................................................. 33
Example:.................................................................................................. 34
Conditions .............................................................................. 35
Syntax:..................................................................................................... 36
Flow Diagram:.......................................................................................... 36
Example 1:............................................................................................... 37
Example 2:............................................................................................... 37
Syntax:..................................................................................................... 38
Flow Diagram:.......................................................................................... 38
Example:.................................................................................................. 39
Syntax:..................................................................................................... 40
Example:.................................................................................................. 40
Syntax:..................................................................................................... 40
Flow Diagram:.......................................................................................... 41
Example:.................................................................................................. 41
Syntax:..................................................................................................... 42iii
Flow Diagram:.......................................................................................... 42
Example:.................................................................................................. 42
Syntax:..................................................................................................... 43
Example:.................................................................................................. 43
Loops ..................................................................................... 44
Syntax:..................................................................................................... 45
Example:.................................................................................................. 45
Syntax:..................................................................................................... 46
Example:.................................................................................................. 46
Syntax:..................................................................................................... 47
Example:.................................................................................................. 47
Reverse FOR LOOP Statement............................................................... 48
Example:.................................................................................................. 49
Labeling a PL/SQL Loop.......................................................................... 50
The Loop Control Statements.................................................................. 51
Syntax:..................................................................................................... 51
Flow Diagram:.......................................................................................... 51
Example:.................................................................................................. 52
The EXIT WHEN Statement .................................................................... 52
Syntax:..................................................................................................... 52
Example:.................................................................................................. 52
Syntax:..................................................................................................... 53
Flow Diagram:.......................................................................................... 53
Example:.................................................................................................. 54
Syntax:..................................................................................................... 54
Flow Diagram:.......................................................................................... 55
Example:.................................................................................................. 55
Restrictions with GOTO Statement.......................................................... 56
Strings.................................................................................... 57
Declaring String Variables ....................................................................... 57
PL/SQL String Functions and Operators ................................................. 58
Example 1................................................................................................ 60
Example 2................................................................................................ 60
Arrays..................................................................................... 62
Creating a Varray Type............................................................................ 62
Example 1................................................................................................ 63
Procedures............................................................................. 65
Parts of a PL/SQL Subprogram ............................................................... 65
Creating a Procedure............................................................................... 66iii
Example:.................................................................................................. 66
Executing a Standalone Procedure ......................................................... 67
Deleting a Standalone Procedure............................................................ 67
Parameter Modes in PL/SQL Subprograms ............................................ 67
IN & OUT Mode Example 1 ..................................................................... 68
IN & OUT Mode Example 2 ..................................................................... 68
Methods for Passing Parameters............................................................. 69
POSITIONAL NOTATION....................................................................... 69
NAMED NOTATION ............................................................................... 69
MIXED NOTATION................................................................................. 69
Functions ............................................................................... 70
Example:.................................................................................................. 71
Calling a Function.................................................................................... 71
Example:.................................................................................................. 72
PL/SQL Recursive Functions................................................................... 72
Cursors .................................................................................. 74
Implicit Cursors........................................................................................ 74
Example:.................................................................................................. 75
Explicit Cursors........................................................................................ 76
Declaring the Cursor................................................................................ 76
Opening the Cursor ................................................................................. 76
Fetching the Cursor ................................................................................. 76
Closing the Cursor................................................................................... 77
Example:.................................................................................................. 77
Records.................................................................................. 78
Table-Based Records .............................................................................. 78
Cursor-Based Records ............................................................................ 79
User-Defined Records ............................................................................. 79
Defining a Record.................................................................................... 80
Accessing Fields...................................................................................... 80
Records as Subprogram Parameters ...................................................... 81
Exceptions ............................................................................. 83
Syntax for Exception Handling................................................................. 83
Example................................................................................................... 83
Raising Exceptions .................................................................................. 84
User-defined Exceptions.......................................................................... 84
Example:.................................................................................................. 85
Pre-defined Exceptions............................................................................ 85
Triggers.................................................................................. 88iii
Benefits of Triggers.................................................................................. 88
Creating Triggers ..................................................................................... 89
Example:.................................................................................................. 89
Triggering a Trigger ................................................................................. 90
Packages ............................................................................... 92
Package Specification ............................................................................. 92
Package Body.......................................................................................... 93
Using the Package Elements................................................................... 93
Example:.................................................................................................. 93
THE PACKAGE SPECIFICATION:......................................................... 94
CREATING THE PACKAGE BODY: ...................................................... 94
USING THE PACKAGE:......................................................................... 95
Collections ............................................................................. 96
Index-By Table......................................................................................... 97
Example:.................................................................................................. 97
Example:.................................................................................................. 98
Nested Tables.......................................................................................... 98
Example:.................................................................................................. 99
Example:.................................................................................................. 99
Collection Methods ................................................................................ 100
Collection Exceptions ............................................................................ 101
Transactions ........................................................................ 103
Starting an Ending a Transaction........................................................... 103
Committing a Transaction...................................................................... 104
Rolling Back Transactions ..................................................................... 104
Savepoints............................................................................................. 104
Automatic Transaction Control............................................................... 105
Date & Time ......................................................................... 106
Field Values for Datetime and Interval Data Types................................ 106
The Datetime Data Types and Functions .............................................. 107
Examples:.............................................................................................. 109
The Interval Data Types and Functions ................................................. 110
DBMS Output....................................................................... 111
DBMS_OUTPUT Subprograms ............................................................. 111
Example:................................................................................................ 112
Object Oriented.................................................................... 113
Instantiating an Object ........................................................................... 114
Member Methods................................................................................... 114
Using Map method................................................................................. 115iii
Using Order method .............................................................................. 116
Inheritance for PL/SQL Objects: ............................................................ 117
Abstract Objects in PL/SQL ................................................................... 119TUTORIALSPOINT
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PL/SQL Overview
This chapter describes the basic definition and concepts PL/SQL:
The PL/SQL programming language was developed by Oracle Corporation in the late
1980s as procedural extension language for SQL and the Oracle relational database. Following
are notable facts about PL/SQL:
 PL/SQL is a completely portable, high-performance transaction-processing language.
 PL/SQL provides a built-in interpreted and OS independent programming environment.
 PL/SQL can also directly be called from the command-line SQL*Plus interface.
 Direct call can also be made from external programming language calls to database.
 PL/SQL's general syntax is based on that of ADA and Pascal programming language.
 Apart from Oracle, PL/SQL is available in TimesTen in-memory database and IBM DB2.
Features of PL/SQL
PL/SQL has the following features:
 PL/SQL is tightly integrated with SQL.
 It offers extensive error checking.
 It offers numerous data types.
 It offers a variety of programming structures.
 It supports structured programming through functions and procedures.
 It supports object oriented programming.
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 It supports developing web applications and server pages.
Advantages of PL/SQL
PL/SQL has the following advantages:
 SQL is the standard database language and PL/SQL is strongly integrated with SQL. PL/SQL
supports both static and dynamic SQL. Static SQL supports DML operations and transaction
control from PL/SQL block. Dynamic SQL is SQL allows embedding DDL statements in PL/SQL
blocks.
 PL/SQL allows sending an entire block of statements to the database at one time. This
reduces network traffic and provides high performance for the applications.
 PL/SQL give high productivity to programmers as it can query, transform, and update data in
a database.
 PL/SQL saves time on design and debugging by strong features, such as exception handling,
encapsulation, data hiding, and object-oriented data types.
 Applications written in PL/SQL are fully portable.
 PL/SQL provides high security level.
 PL/SQL provides access to predefined SQL packages.
 PL/SQL provides support for Object-Oriented Programming.
 PL/SQL provides support for Developing Web Applications and Server Pages.TUTORIALSPOINT
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Environment
This chapter describes the environment setup for starting with PL/SQl:
PL/SQL is not a stand-alone 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 Oracle RBDMS Server installed in your machine
which will take care of executing SQL commands. 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
You will have to download either 32bit or 64 bit version of the installation as per your operating
system. Usually there are two files, as I have downloaded for 64 bit Windows7. You will also use
similar steps on your operating system, does not matter if it is Linux or Solaris.
 win64_11gR2_database_1of2.zip
 win64_11gR2_database_2of2.zip
After donwloading above two files, you will need to unzip them in a single
directory database and under that you will find following sub-directories:
Step 1
Now let's launch Oracle Database Installer using setup file. Following is the first screen. You can
provide your email ID and uncheck, check box and click Next button:
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Step 2
You will have following screen, just uncheck the check box and click continue button to
proceed.
Step 3
Just select first option Create and Configure Database using radio button and click Next button
to proceed:TUTORIALSPOINT
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Step 4
I assume you are installing Oracle just for learning purpose and you will install it on your PC or
Laptop. So select Desktop Class option and click Next button to proceed:TUTORIALSPOINT
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Step 5
Provide a location where you will install Oracle Server. Just modify Oracle Base and rest of the
locations will set automatically. Second you will have to provide a password which will be used
by system DBA. Once you provide required information, click Next button to proceed:
Step 6
Just click Next button to proceed:TUTORIALSPOINT
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Step 7
Now click Finish button to proceed, this will start actuall server installation.
Step 8
Just wait, until Oracle starts doing required configuration.TUTORIALSPOINT
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Step 9
Here Oracle installation will copy required configuration files, so kindly just wait and watch:TUTORIALSPOINT
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Step 10
Once everything is done, you will have following dialogue box. Just click OK button and come
out.TUTORIALSPOINT
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Step 11
Once your installation is done, you will have following final window.TUTORIALSPOINT
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Final Step
If everything has been done successfully then its time to verify your installation. At your
command prompt use the following command if you are using Windows:
sqlplus "/ as sysdba"
If everything is fine, you should have SQL prompt where you will write your PL/SQL commands
and scripts:TUTORIALSPOINT
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Text Editor
Running large programs from command prompt may land you in inadvertently losing some of the
work. So a better option is to use command files. To use the command files:
 Type your code in a text editor, like Notepad, Notepad+, or EditPlus etc.
 Save the file with the .sql extension in the home directory.
 Launch SQL*Plus command prompt from the directory where you created your PL/SQL file.
 Type @file_name at the SQL*Plus command prompt to execute your program.
If you are not using a file to execute PL/SQL scripts, then simply copy your PL/SQL code and
then right click on the black window having SQL prompt and use paste option to paste complete
code at the command prompt. Finally, just press enter to execute the code, if it is not already
executed.TUTORIALSPOINT
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Basic Syntax
This chapter describes the basic syntax followed:
PL/SQL is a block-structured language, meaning that PL/SQL programs are divided and
written in logical blocks of code. Each block consists of three sub-parts:
S.N. 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 section starts with the keyword EXCEPTION. This section is again optional
and contains exception(s) that handle errors in the program.
Every PL/SQL statement end with a semicolon (;). PL/SQL blocks can be nested within other
PL/SQL blocks using BEGIN and END. Here is the basic structure of a PL/SQL block:
DECLARE
<declarations section>
BEGIN
<executable command(s)>
EXCEPTION
<exception handling>
END;
The 'Hello World' Example:
DECLARE
message varchar2(20):= 'Hello, World!';
BEGIN
dbms_output.put_line(message);
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END;
/
The end; line signals the end of the PL/SQL block. To run the code from 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 SQL prompt, it produces following result:
Hello World
PL/SQL procedure successfully completed.
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
A delimiter is a symbol with a special meaning. Following is the list of delimiters in PL/SQL:
Delimiter Description
+, -, *, / Addition, subtraction/negation, multiplication, division
% Attribute indicator
' Character string delimiter
. Component selector
(,) Expression or list delimiter
: Host variable indicator
, Item separator
" Quoted identifier delimiter
= Relational operator
@ Remote access indicator
; Statement terminator
:= Assignment operator
=> Association operator
|| Concatenation operator
** Exponentiation operator
<<, >> Label delimiter (begin and end)TUTORIALSPOINT
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/*, */ Multi-line comment delimiter (begin and end)
-- Single-line comment indicator
.. Range operator
<, >, <=, >= Relational operators
<>, '=, ~=, ^= Different versions of NOT EQUAL
The PL/SQL Comments
Program comments are explanatory statements that you can include in the PL/SQL code that
you write and helps anyone reading it's source code. All programming languages allow for some
form of comments.
The PL/SQL supports single line and multi-line comments. All characters available inside any
comment are ignored by 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;
/
When the above code is executed at SQL prompt, it produces following result:
Hello World
PL/SQL procedure successfully completed.
PL/SQL Program Units
A PL/SQL unit is any one of the following:
 PL/SQL block
 Function
 Package
 Package body
 Procedure
 TriggerTUTORIALSPOINT
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 Type
 Type body
Each of these units will be discussed in the forthcoming chapters.TUTORIALSPOINT
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Data Types
This chapter describes the Data Types used under PL/SQL:.
PL/SQL variables, constants and parameters must have a valid data types which specifies
a storage format, constraints, and valid range of values. This tutorial will take you
through SCALAR and LOB data types available in PL/SQL and other two data types will be
covered in other chapters.
Category Description
Scalar Single values with no internal components, such as a NUMBER, DATE,
or BOOLEAN.
Large Object (LOB) Pointers to large objects that are stored separately from other data
items, such as text, graphic images, video clips, and sound waveforms.
Composite Data items that have internal components that can be accessed
individually. For example, collections and records.
Reference Pointers to other data items.
PL/SQL Scalar Data Types and Subtypes
PL/SQL Scalar Data Types and Subtypes come under the following categories:
Date Type Description
Numeric Numeric values, on which arithmetic operations are performed.
Character Alphanumeric values that represent single characters or strings of
characters.
Boolean Logical values, on which logical operations are performed.
Datetime Dates and times.
PL/SQL provides subtypes of data types. For example, the data type NUMBER has a subtype
called INTEGER. You can use subtypes in your PL/SQL program to make the data types
compatible with data types in other programs while embedding PL/SQL code in another
program, such as a Java program.
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PL/SQL Numeric Data Types and Subtypes
Following is the detail of PL/SQL pre-defined numeric data types and their sub-types:
Data Type Description
PLS_INTEGER Signed integer in range -2,147,483,648 through 2,147,483,647,
represented in 32 bits
BINARY_INTEGER Signed integer in range -2,147,483,648 through 2,147,483,647,
represented in 32 bits
BINARY_FLOAT Single-precision IEEE 754-format floating-point number
BINARY_DOUBLE Double-precision IEEE 754-format floating-point number
NUMBER(prec, scale) Fixed-point or floating-point number with absolute value in range 1E-130
to (but not including) 1.0E126. A NUMBER variable can also represent 0.
DEC(prec, scale) ANSI specific fixed-point type with maximum precision of 38 decimal
digits.
DECIMAL(prec, scale) IBM specific fixed-point type with maximum precision of 38 decimal digits.
NUMERIC(pre, secale) Floating type with maximum precision of 38 decimal digits.
DOUBLE PRECISION ANSI specific floating-point type with maximum precision of 126 binary
digits (approximately 38 decimal digits)
FLOAT ANSI and IBM specific floating-point type with maximum precision of 126
binary digits (approximately 38 decimal digits)
INT ANSI specific integer type with maximum precision of 38 decimal digits
INTEGER ANSI and IBM specific integer type with maximum precision of 38
decimal digits
SMALLINT ANSI and IBM specific integer type with maximum precision of 38
decimal digits
REAL Floating-point type with maximum precision of 63 binary digits
(approximately 18 decimal digits)
Following is a valid declaration:
DECLARE
num1 INTEGER;
num2 REAL;
num3 DOUBLE PRECISION;
BEGIN
null;
END;
/
When the above code is compiled and executed, it produces following result:
PL/SQL procedure successfully completedTUTORIALSPOINT
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PL/SQL Character Data Types and Subtypes
Following is the detail of PL/SQL pre-defined character data types and their sub-types:
Data Type Description
CHAR Fixed-length character string with maximum size of 32,767 bytes
VARCHAR2 Variable-length character string with maximum size of 32,767 bytes
RAW Variable-length binary or byte string with maximum size of 32,767
bytes, not interpreted by PL/SQL
NCHAR Fixed-length national character string with maximum size of 32,767
bytes
NVARCHAR2 Variable-length national character string with maximum size of 32,767
bytes
LONG Variable-length character string with maximum size of 32,760 bytes
LONG RAW Variable-length binary or byte string with maximum size of 32,760
bytes, not interpreted by PL/SQL
ROWID Physical row identifier, the address of a row in an ordinary table
UROWID Universal row identifier (physical, logical, or foreign row identifier)
PL/SQL Boolean Data Types
The BOOLEAN data type stores logical values that are used in logical operations. The logical
values are the Boolean values TRUE and FALSE and the value NULL.
However, SQL has no data type equivalent to BOOLEAN. Therefore Boolean values cannot be
used in:
 SQL statements
 Built-in SQL functions (such as TO_CHAR)
 PL/SQL functions invoked from SQL statements
PL/SQL Datetime and Interval Types
The DATE datatype to store fixed-length datetimes, which include the time of day in seconds
since midnight. Valid dates range from January 1, 4712 BC to December 31, 9999 AD.
The default date format is set by the Oracle initialization parameter NLS_DATE_FORMAT. For
example, the default might be 'DD-MON-YY', which includes a two-digit number for the day of
the month, an abbreviation of the month name, and the last two digits of the year, for example,
01-OCT-12.
Each DATE includes the century, year, month, day, hour, minute, and second. The following
table shows the valid values for each field:TUTORIALSPOINT
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Field Name Valid Datetime Values Valid Interval Values
YEAR -4712 to 9999
(excluding year 0) Any nonzero integer
MONTH 01 to 12 0 to 11
DAY
01 to 31 (limited by the
values of MONTH and
YEAR, according to the
rules of the calendar
for the locale)
Any nonzero integer
HOUR 00 to 23 0 to 23
MINUTE 00 to 59 0 to 59
SECOND
00 to 59.9(n), where
9(n) is the precision of
time fractional seconds
0 to 59.9(n), where 9(n) is the precision of
interval fractional seconds
TIMEZONE_HOUR
-12 to 14 (range
accommodates daylight
savings time changes)
Not applicable
TIMEZONE_MINUTE 00 to 59 Not applicable
TIMEZONE_REGION
Found in the dynamic
performance view
V$TIMEZONE_NAMES
Not applicable
TIMEZONE_ABBR
Found in the dynamic
performance view
V$TIMEZONE_NAMES
Not applicable
PL/SQL Large Object (LOB) Data Types
Large object (LOB) data types refer large to data items such as text, graphic images, video clips,
and sound waveforms. LOB data types allow efficient, random, piecewise access to this data.
Following are the predefined PL/SQL LOB data types:
Data Type Description Size
BFILE
Used to store large binary
objects in operating system
files outside the database.
System-dependent. Cannot exceed 4 gigabytes
(GB).
BLOB Used to store large binary
objects in the database. 8 to 128 terabytes (TB)
CLOB
Used to store large blocks of
character data in the
database.
8 to 128 TB
NCLOB
Used to store large blocks of
NCHAR data in the
database.
8 to 128 TBTUTORIALSPOINT
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PL/SQL User-Defined Subtypes
A subtype is a subset of another data type, which is called its base type. A subtype has the
same valid operations as its base type, but only a subset of its valid values.
PL/SQL predefines several subtypes in package STANDARD. For example, PL/SQL predefines
the subtypes CHARACTER and INTEGER as follows:
SUBTYPE CHARACTER IS CHAR;
SUBTYPE INTEGER IS NUMBER(38,0);
You can define and use your own subtypes. The following program illustrates defining and using
a user-defined subtype:
DECLARE
SUBTYPE name IS char(20);
SUBTYPE message IS varchar2(100);
salutation name;
greetings message;
BEGIN
salutation := 'Reader ';
greetings := 'Welcome to the World of PL/SQL';
dbms_output.put_line('Hello ' || salutation || greetings);
END;
/
When the above code is executed at SQL prompt, it produces following result:
Hello Reader Welcome to the World of PL/SQL
PL/SQL procedure successfully completed.
NULLs in PL/SQL
PL/SQL NULL values represent missing or unknown data and they are not an integer, a
character, or any other specific data type. Note that NULL is not the same as an empty data
string or the null character value '\0'. A null can be assigned but it cannot be equated with
anything, including itself.TUTORIALSPOINT
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Variables
This chapter describes the variables used:
Avariable is nothing but a name given to a storage area that our programs can
manipulate. Each variable in PL/SQL has a specific data type, which determines the size and
layout of the variable's memory; the range of values that can be stored within that memory and
the set of operations that can be applied to the variable.
The name of a PL/SQL variable consist of a letter optionally followed by more letters, numerals,
dollar signs, underscores, and number signs and should not exceed 30 characters. By default,
variable names are not case-sensitive. You cannot use a reserved PL/SQL keywords as a
variable name.
PL/SQL programming language allows to define various type of variables which we will cover in
subsequent chapters like date time data types, records, collections etc. For this chapter, let us
study only basic variable types.
Variable Declaration in PL/SQL
PL/SQL variables must be declared in the declaration section or in a package as a global
variable. When you declare a variable, PL/SQL allocates memory for the variable's value and the
storage location is identified by the variable name.
The syntax for declaring a variable is:
variable_name [CONSTANT] datatype [NOT NULL] [:= | DEFAULT initial_value]
Where, variable_name is a valid identifier in PL/SQL, datatype must be a valid PL/SQL data type
or any user defined data type which we already have discussed in last chapter. Some valid
variable declarations along with their definition are shown below:
sales number(10, 2);
pi CONSTANT double precision := 3.1415;
name varchar2(25);
address varchar2(100);
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When you provide a size, scale or precision limit with the data type, it is called a constrained
declaration. Constrained declarations require less memory than unconstrained declarations, For
example:
sales number(10, 2);
name varchar2(25);
address varchar2(100);
Initializing Variables in PL/SQL
Whenever you declare a variable, PL/SQL assigns it a default value of NULL. If you want to
initialize a variable with a value other than the NULL value, you can do so during the declaration,
using either of the following:
 The DEFAULT keyword
 The assignment operator
For example:
counter binary_integer := 0;
greetings varchar2(20) DEFAULT 'Have a Good Day';
You can also specify that a variable should not have a NULL value using the NOT
NULL constraint. If you use the NOT NULL constraint, you must explicitly assign an initial value
for that variable.
It is a good programming practice to initialize variables properly otherwise, sometime program
would produce unexpected result. Try following example which makes use of various types of
variables:
DECLARE
a integer := 10;
b integer := 20;
c integer;
f real;
BEGIN
c := a + b;
dbms_output.put_line('Value of c: ' || c);
f := 70.0/3.0;
dbms_output.put_line('Value of f: ' || f);
END;
/
When the above code is executed, it produces following result:
Value of c: 30
Value of f: 23.333333333333333333
PL/SQL procedure successfully completed.
Variable Scope in PL/SQL
PL/SQL allows the nesting of Blocks i.e., each program block may contain another inner block. If
a variable is declared within an inner block, it is not accessible to the outer block. However, if a TUTORIALSPOINT
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variable is declared and accessible to an outer Block, it is also accessible to all nested inner
Blocks. There are two types of variable scope:
 Local variables - variables declared in an inner block and not accessible to outer blocks.
 Global variables - variables declared in the outermost block or a package.
Following example shows the usage of Local and Global variables in its simple form:
DECLARE
-- Global variables
num1 number := 95;
num2 number := 85;
BEGIN
dbms_output.put_line('Outer Variable num1: ' || num1);
dbms_output.put_line('Outer Variable num2: ' || num2);
DECLARE
-- Local variables
num1 number := 195;
num2 number := 185;
BEGIN
dbms_output.put_line('Inner Variable num1: ' || num1);
dbms_output.put_line('Inner Variable num2: ' || num2);
END;
END;
/
When the above code is executed, it produces following result:
Outer Variable num1: 95
Outer Variable num2: 85
Inner Variable num1: 195
Inner Variable num2: 185
PL/SQL procedure successfully completed.
Assigning SQL Query Results to PL/SQL Variables
You can use the SELECT INTO statement of SQL to assign values to PL/SQL variables. For
each item in the SELECT list, there must be a corresponding, type-compatible variable in the
INTO list. The following example illustrates the concept: Let us create a table named
CUSTOMERS:
(For SQL statements please look at the SQL tutorial)
CREATE TABLE CUSTOMERS(
ID INT NOT NULL,
NAME VARCHAR (20) NOT NULL,
AGE INT NOT NULL,
ADDRESS CHAR (25),
SALARY DECIMAL (18, 2),
PRIMARY KEY (ID)
);
Table Created
Next, let us insert some values in the table:TUTORIALSPOINT
Simply Easy Learning Page 25
INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (1, 'Ramesh', 32, 'Ahmedabad', 2000.00 );
INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (2, 'Khilan', 25, 'Delhi', 1500.00 );
INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (3, 'kaushik', 23, 'Kota', 2000.00 );
INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (4, 'Chaitali', 25, 'Mumbai', 6500.00 );
INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (5, 'Hardik', 27, 'Bhopal', 8500.00 );
INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY)
VALUES (6, 'Komal', 22, 'MP', 4500.00 );
The following program assigns values from the above table to PL/SQL variables using the
SELECT INTO clause of SQL:
DECLARE
c_id customers.id%type := 1;
c_name customers.name%type;
c_addr customers.address%type;
c_sal customers.salary%type;
BEGIN
SELECT name, address, salary INTO c_name, c_addr, c_sal
FROM customers
WHERE id = c_id;
dbms_output.put_line
('Customer ' ||c_name || ' from ' || c_addr || ' earns ' || c_sal);
END;
/
When the above code is executed, it produces following result:
Customer Ramesh from Ahmedabad earns 2000
PL/SQL procedure completed successfullyTUTORIALSPOINT
Simply Easy Learning Page 26
Constants
This chapter shows the usage of constants:
Aconstant holds a value that once declared, does not change in the program. A
constant declaration specifies its name, data type, and value, and allocates storage for it. The
declaration can also impose the NOT NULL constraint.
Declaring a Constant
A constant is declared using the CONSTANT keyword. It requires an initial value and does not
allow that value to be changed, For example:
PI CONSTANT NUMBER := 3.141592654;
DECLARE
-- constant declaration
pi constant number := 3.141592654;
-- other declarations
radius number(5,2);
dia number(5,2);
circumference number(7, 2);
area number (10, 2);
BEGIN
-- processing
radius := 9.5;
dia := radius * 2;
circumference := 2.0 * pi * radius;
area := pi * radius * radius;
-- output
dbms_output.put_line('Radius: ' || radius);
dbms_output.put_line('Diameter: ' || dia);
dbms_output.put_line('Circumference: ' || circumference);
dbms_output.put_line('Area: ' || area);
END;
/
When the above code is executed at SQL prompt, it produces the following result:
Radius: 9.5
Diameter: 19
CHAPTER
6TUTORIALSPOINT
Simply Easy Learning Page 27
Circumference: 59.69
Area: 283.53
Pl/SQL procedure successfully completed.
The PL/SQL Literals
A literal is an explicit numeric, character, string, or Boolean value not represented by an
identifier. For example, TRUE, 786, NULL, 'tutorialspoint' are all literals of type Boolean, number,
or string. PL/SQL, literals are case-sensitive. PL/SQL supports the following kinds of literals:
 Numeric Literals
 Character Literals
 String Literals
 BOOLEAN Literals
 Date and Time Literals
The following table provides examples from all these categories of literal values.
Literal Type Example:
Numeric Literals
050 78 -14 0 +32767
6.6667 0.0 -12.0 3.14159 +7800.00
6E5 1.0E-8 3.14159e0 -1E38 -9.5e-3
Character Literals 'A' '%' '9' ' ' 'z' '('
String Literals
'Hello, world!'
'Tutorials Point'
'19-NOV-12'
BOOLEAN Literals TRUE, FALSE, and NULL.
Date and Time Literals DATE '1978-12-25';
TIMESTAMP '2012-10-29 12:01:01';
To embed single quotes within a string literal, place two single quotes next to each other as
shown below:
DECLARE
message varchar2(20):= ''That''s tutorialspoint.com!'';
BEGIN
dbms_output.put_line(message);
END;
/
When the above code is executed at SQL prompt, it produces following result:
That's tutorialspoint.com!
PL/SQL procedure successfully completed.TUTORIALSPOINT
Simply Easy Learning Page 28
Operators
This chapter describes the different operators used under PL/SQL:
An operator is a symbol that tells the compiler to perform specific mathematical or
logical manipulations. PL/SQL language is rich in built-in operators and provides following type
of operators:
 Arithmetic operators
 Relational operators
 Comparison operators
 Logical operators
 String operators
This tutorial will explain the arithmetic, relational, comparison and logical operators one by one.
The String operators will be discussed under the chapter: PL/SQL - Strings.
Arithmetic Operators
Following table shows all the arithmetic operators supported by PL/SQL. Assume variable A
holds 10 and variable B holds 5 then:
Operator Description Example
+ Adds two operands A + B will give 15
- Subtracts second operand from the first A - B will give 5
* Multiply both operands A * B will give 50
/ Divide numerator by de-numerator A / B will give 2
** Exponentiation operator, raises one operand to the power of other A ** B will give
100000
CHAPTER
7TUTORIALSPOINT
Simply Easy Learning Page 29
Example:
BEGIN
dbms_output.put_line( 10 + 5);
dbms_output.put_line( 10 - 5);
dbms_output.put_line( 10 * 5);
dbms_output.put_line( 10 / 5);
dbms_output.put_line( 10 ** 5);
END;
/
When the above code is executed at SQL prompt, it produces the following result:
15
5
50
2
100000
PL/SQL procedure successfully completed.
Relational Operators
Relational operators compare two expressions or values and return a Boolean result. Following
table shows all the relational operators supported by PL/SQL. Assume variable A holds 10 and
variable B holds 20 then:
Operator Description Example
=
Checks if the value of two operands is equal or not, if yes then
condition becomes true.
(A = B) is not
true.
!=
<>
~=
Checks if the value of two operands is equal or not, if values are not
equal then condition becomes true.
(A != B) is
true.
>
Checks if the value of left operand is greater than the value of right
operand, if yes then condition becomes true.
(A > B) is not
true.
<
Checks if the value of left operand is less than the value of right
operand, if yes then condition becomes true. (A < B) is true.
>= Checks if the value of left operand is greater than or equal to the
value of right operand, if yes then condition becomes true.
(A >= B) is not
true.
<= Checks if the value of left operand is less than or equal to the value
of right operand, if yes then condition becomes true.
(A <= B) is
true.
Example:
DECLARE
a number (2) := 21;
b number (2) := 10;
BEGIN
IF (a = b) then
dbms_output.put_line('Line 1 - a is equal to b');
ELSE
dbms_output.put_line('Line 1 - a is not equal to b');
END IF;TUTORIALSPOINT
Simply Easy Learning Page 30
IF (a < b) then
dbms_output.put_line('Line 2 - a is less than b');
ELSE
dbms_output.put_line('Line 2 - a is not less than b');
END IF;
IF ( a > b ) THEN
dbms_output.put_line('Line 3 - a is greater than b');
ELSE
dbms_output.put_line('Line 3 - a is not greater than b');
END IF;
-- Lets change value of a and b
a := 5;
b := 20;
IF ( a <= b ) THEN
dbms_output.put_line('Line 4 - a is either equal or less than b');
END IF;
IF ( b >= a ) THEN
dbms_output.put_line('Line 5 - b is either equal or greater than a');
END IF;
IF ( a <> b ) THEN
dbms_output.put_line('Line 6 - a is not equal to b');
ELSE
dbms_output.put_line('Line 6 - a is equal to b');
END IF;
END;
/
When the above code is executed at SQL prompt, it produces the following result:
Line 1 - a is not equal to b
Line 2 - a is not less than b
Line 3 - a is greater than b
Line 4 - a is either equal or less than b
Line 5 - b is either equal or greater than a
Line 6 - a is not equal to b
PL/SQL procedure successfully completed
Comparison Operators
Comparison operators are used for comparing one expression to another. The result is always
either TRUE, FALSE, OR NULL.
Operator Description Example
LIKE
The LIKE operator compares a character, string, or CLOB
value to a pattern and returns TRUE if the value matches
the pattern and FALSE if it does not.
If 'Zara Ali' like 'Z%
A_i' returns a
Boolean true,
whereas, 'Nuha Ali'
like 'Z% A_i' returns a
Boolean false.
BETWEEN The BETWEEN operator tests whether a value lies in a
specified range. x BETWEEN a AND b means that x >= a
If x = 10 then, x
between 5 and 20 TUTORIALSPOINT
Simply Easy Learning Page 31
and x <= b. returns true, x
between 5 and 10
returns true, but x
between 11 and 20
returns false.
IN The IN operator tests set membership. x IN (set) means that
x is equal to any member of set.
If x = 'm' then, x in
('a', 'b', 'c') returns
boolean false but x in
('m', 'n', 'o') returns
Boolean true.
IS NULL
The IS NULL operator returns the BOOLEAN value TRUE if
its operand is NULL or FALSE if it is not NULL.
Comparisons involving NULL values always yield NULL.
If x = 'm', then 'x is
null' returns Boolean
false.
LIKE Operator:
This program tests the LIKE operator, though you will learn how to write procedure in PL/SQL,
but I'm going to use a small procedure() to show the functionality of LIKE operator:
DECLARE
PROCEDURE compare (value varchar2, pattern varchar2 ) is
BEGIN
IF value LIKE pattern THEN
dbms_output.put_line ('True');
ELSE
dbms_output.put_line ('False');
END IF;
END;
BEGIN
compare('Zara Ali', 'Z%A_i');
compare('Nuha Ali', 'Z%A_i');
END;
/
When the above code is executed at SQL prompt, it produces following result:
True
False
PL/SQL procedure successfully completed.
BETWEEN Operator:
The following program shows the usage of the BETWEEN operator:
DECLARE
x number(2) := 10;
BEGIN
IF (x between 5 and 20) THEN
dbms_output.put_line('True');
ELSE
dbms_output.put_line('False');
END IF;
IF (x BETWEEN 5 AND 10) THEN
dbms_output.put_line('True');TUTORIALSPOINT
Simply Easy Learning Page 32
ELSE
dbms_output.put_line('False');
END IF;
IF (x BETWEEN 11 AND 20) THEN
dbms_output.put_line('True');
ELSE
dbms_output.put_line('False');
END IF;
END;
/
When the above code is executed at SQL prompt, it produces following result:
True
True
False
PL/SQL procedure successfully completed.
IN and IS NULL Operators:
The following program shows the usage of IN and IS NULL operators:
DECLARE
letter varchar2(1) := 'm';
BEGIN
IF (letter in ('a', 'b', 'c')) THEN
dbms_output.put_line('True');
ELSE
dbms_output.put_line('False');
END IF;
IF (letter in ('m', 'n', 'o')) THEN
dbms_output.put_line('True');
ELSE
dbms_output.put_line('False');
END IF;
IF (letter is null) THEN
dbms_output.put_line('True');
ELSE
dbms_output.put_line('False');
END IF;
END;
/
When the above code is executed at SQL prompt, it produces following result:
False
True
False
PL/SQL procedure successfully completed.TUTORIALSPOINT
Simply Easy Learning Page 33
Logical Operators
Following table shows the Logical operators supported by PL/SQL. All these operators work on
Boolean operands and produces Boolean results. Assume variable A holds true and variable B
holds false then:
Operator Description Example
and Called logical AND operator. If both the operands are true then
condition becomes true.
(A and B) is
false.
or
Called logical OR Operator. If any of the two operands is true then
condition becomes true. (A or B) is true.
not
Called logical NOT Operator. Used to reverse the logical state of its
operand. If a condition is true then Logical NOT operator will make
it false.
not (A and B) is
true.
Example:
DECLARE
a boolean := true;
b boolean := false;
BEGIN
IF (a AND b) THEN
dbms_output.put_line('Line 1 - Condition is true');
END IF;
IF (a OR b) THEN
dbms_output.put_line('Line 2 - Condition is true');
END IF;
IF (NOT a) THEN
dbms_output.put_line('Line 3 - a is not true');
ELSE
dbms_output.put_line('Line 3 - a is true');
END IF;
IF (NOT b) THEN
dbms_output.put_line('Line 4 - b is not true');
ELSE
dbms_output.put_line('Line 4 - b is true');
END IF;
END;
/
When the above code is executed at SQL prompt, it produces the following result:
Line 2 - Condition is true
Line 3 - a is true
Line 4 - b is not true
PL/SQL procedure successfully completed.
PL/SQL Operator Precedence
Operator precedence determines the grouping of terms in an expression. This affects how an
expression is evaluated. Certain operators have higher precedence than others; for example, the
multiplication operator has higher precedence than the addition operator:TUTORIALSPOINT
Simply Easy Learning Page 34
For example x = 7 + 3 * 2; Here x is assigned 13, not 20 because operator * has higher
precedence than + so it first get multiplied with 3*2 and then adds into 7.
Here operators with the highest precedence appear at the top of the table, those with the lowest
appear at the bottom. Within an expression, higher precedence operators will be evaluated first.
Operator Operation
** exponentiation
+, - identity, negation
*, / multiplication, division
+, -, || addition, subtraction, concatenation
=, <, >, <=, >=, <>, !=, ~=, ^=,
IS NULL, LIKE, BETWEEN, IN comparison
NOT logical negation
AND conjunction
OR inclusion
Example:
Try following example to understand the operator precedence available in PL/SQL:
DECLARE
a number(2) := 20;
b number(2) := 10;
c number(2) := 15;
d number(2) := 5;
e number(2) ;
BEGIN
e := (a + b) * c / d; -- ( 30 * 15 ) / 5
dbms_output.put_line('Value of (a + b) * c / d is : '|| e );
e := ((a + b) * c) / d; -- (30 * 15 ) / 5
dbms_output.put_line('Value of ((a + b) * c) / d is : ' || e );
e := (a + b) * (c / d); -- (30) * (15/5)
dbms_output.put_line('Value of (a + b) * (c / d) is : '|| e );
e := a + (b * c) / d; -- 20 + (150/5)
dbms_output.put_line('Value of a + (b * c) / d is : ' || e );
END;
/
When the above code is executed at SQL prompt, it produces the following result:
Value of (a + b) * c / d is : 90
Value of ((a + b) * c) / d is : 90
Value of (a + b) * (c / d) is : 90
Value of a + (b * c) / d is : 50
PL/SQL procedure successfully completed.TUTORIALSPOINT
Simply Easy Learning Page 35
Conditions
This chapter describes the Decision Making Structure:
Decision making structures require that the programmer specify one or more conditions
to be evaluated or tested by the program, along with a statement or statements to be executed if
the condition is determined to be true, and optionally, other statements to be executed if the
condition is determined to be false.
Following is the general from of a typical conditional (i.e. decision making) structure found in
most of the programming languages:
PL/SQL programming language provides following types of decision making statements. Click
the following links to check their detail.
CHAPTER
8TUTORIALSPOINT
Simply Easy Learning Page 36
Statement Description
IF - THEN statement
The IF statement associates a condition with a sequence of
statements enclosed by the keywords THEN and END IF. If
the condition is true, the statements get executed and if the
condition is false or NULL then the IF statement does nothing.
IF-THEN-ELSE statement
IF statement adds the keyword ELSE followed by an
alternative sequence of statement. If the condition is false or
NULL , then only the alternative sequence of statements get
executed. It ensures that either of the sequence of statements
is executed.
IF-THEN-ELSIF statement It allows you to choose between several alternatives.
Case statement
Like the IF statement, the CASE statement selects one
sequence of statements to execute. However, to select the
sequence, the CASE statement uses a selector rather than
multiple Boolean expressions. A selector is an expression
whose value is used to select one of several alternatives.
Searched CASE statement
The searched CASE statement has no selector, and it's
WHEN clauses contain search conditions that yield Boolean
values.
nested IF-THEN-ELSE You can use one IF-THEN or IF-THEN-ELSIF statement
inside another IF-THEN or IF-THEN-ELSIF statement(s).
IF - THEN statement
It is the simplest form of IF control statement, frequently used in decision making and changing
the control flow of the program execution.
The IF statement associates a condition with a sequence of statements enclosed by the
keywordsTHEN and END IF. If the condition is TRUE, the statements get executed and if the
condition is FALSE orNULL then the IF statement does nothing.
Syntax:
Syntax for IF-THEN statement is:
IF condition THEN
S;
END IF;
Where condition is a Boolean or relational condition and S is a simple or compound statement.
Example of an IF-THEN statement is:
IF (a <= 20) THEN
c:= c+1;
END IF;
If the boolean expression condition evaluates to true then the block of code inside the if
statement will be executed. If boolean expression evaluates to false then the first set of code
after the end of the if statement (after the closing end if) will be executed.
Flow Diagram:TUTORIALSPOINT
Simply Easy Learning Page 37
Example 1:
Let us try a complete example that would illustrate the concept:
DECLARE
a number(2) := 10;
BEGIN
a:= 10;
-- check the boolean condition using if statement
IF( a < 20 ) THEN
-- if condition is true then print the following
dbms_output.put_line('a is less than 20 ' );
END IF;
dbms_output.put_line('value of a is : ' || a);
END;
/
When the above code is executed at SQL prompt, it produces the following result:
a is less than 20
value of a is : 10
PL/SQL procedure successfully completed.
Example 2:
Consider we have a table and few records in the table as we had created in PL/SQL Variable
Types
DECLARE
c_id customers.id%type := 1;
c_sal customers.salary%type;TUTORIALSPOINT
Simply Easy Learning Page 38
BEGIN
SELECT salary
INTO c_sal
FROM customers
WHERE id = c_id;
IF (c_sal <= 2000) THEN
UPDATE customers
SET salary = salary + 1000
WHERE id = c_id;
dbms_output.put_line ('Salary updated');
END IF;
END;
/
When the above code is executed at SQL prompt, it produces the following result:
Salary updated
PL/SQL procedure successfully completed.
IF-THEN-ELSE statement
A sequence of IF-THEN statements can be followed by an optional sequence
of ELSE statements, which executes when the condition is FALSE.
Syntax:
Syntax for the IF-THEN-ELSE statement is:
IF condition THEN
S1;
ELSE
S2;
END IF;
Where, S1 and S2 are different sequence of statements. In the IF-THEN-ELSE statements,
when the test condition is TRUE, the statement S1 is executed and S2 is skipped; when the
test condition is FALSE, then S1 is bypassed and statement S2 is executed, For example,
IF color = red THEN
dbms_output.put_line('You have chosen a red car')
ELSE
dbms_output.put_line('Please choose a color for your car');
END IF;
If the boolean expression condition evaluates to true then the if-then block of code will be
executed otherwise the else block of code will be executed.
Flow Diagram:TUTORIALSPOINT
Simply Easy Learning Page 39
Example:
Let us try a complete example that would illustrate the concept:
DECLARE
a number(3) := 100;
BEGIN
-- check the boolean condition using if statement
IF( a < 20 ) THEN
-- if condition is true then print the following
dbms_output.put_line('a is less than 20 ' );
ELSE
dbms_output.put_line('a is not less than 20 ' );
END IF;
dbms_output.put_line('value of a is : ' || a);
END;
/
When the above code is executed at SQL prompt, it produces the following result:
a is not less than 20
value of a is : 100
PL/SQL procedure successfully completed.
IF-THEN-ELSIF statement
The IF-THEN-ELSIF statement allows you to choose between several alternatives. An IFTHEN statement can be followed by an optional ELSIF...ELSE statement. The ELSIF clause lets
you add additional conditions.
When using IF-THEN-ELSIF statements there are few points to keep in mind.
 Its ELSIF not ELSEIF