Chapter 1

Introduction to PL/SQL15

Chapter 1

Introduction to PL/SQL

Need for PL/SQL
Benefits of Using PL/SQL
PL/SQL Block Types and Constructs
PL/SQL Block Structure
Operators and SQL Functions in PL/SQL
Variables
Nested Blocks

© SQL Star International Ltd 1


Objectives

At the end of this chapter, you will be able to:

 State the need for a procedural language in Oracle

 Create PL/SQL blocks

 Write nested blocks



Introducing PL/SQL
In the journey so far, you have learnt about the Structured Query Language (SQL).
The Oracle software provides a language, Procedural Language/SQL (PL/SQL), which
is an extension of SQL.

PL/SQL implements modularity in the codes you write. It allows you to perform
iterations and handle errors. Features like data hiding and error handling make
PL/SQL a state-of-the-art language for databases.

PL/SQL also allows data manipulation and SQL query statements to be included
within procedural units of code. This makes PL/SQL a powerful transaction processing
mechanism.

Need for PL/SQL
The requirement for PL/SQL was mainly due to the need to centralize automated
business tasks. For example, if each employee in an organization maintains separate
programs to manage their tasks and updates them at their discretion, it could create
confusions, such as:

• New employees or existing employees who are handed over someone else’s
work, would have a problem understanding the process followed by
the employee vis-à-vis the organization

• Any change in business policy or functionality would have to be updated by all
the employees individually in all relevant programs.

In a centralized functionality this is avoided because all changes need to be made at
one place. Changes will get reflected in the relevant codes and all users can access
updated information.

Benefits of Using PL/SQL
The reasons for using PL/SQL are as follows:

 Integrating with the Oracle server and Oracle development tools
 Implementing performance enhancements in an application
 Modularizing the development of programs
 Implementing Portability
 Declaration of variables
 Programming with procedural language control structures
 Handling errors



Integration

PL/SQL plays a key role in:

 Oracle server, through stored procedures and functions, database triggers and
packages
 Oracle development tools, through Oracle Developer component triggers

PL/SQL supports the use of SQL datatypes. With direct access provided by SQL,
these shared datatypes integrate PL/SQL with the Oracle server data dictionary.
Hence, PL/SQL successfully bridges the gap between access to database technology
and the need for procedural language capabilities.

Most applications such as Oracle Forms, Oracle Reports and Oracle Graphics, use
shared libraries (that hold code), which can be accessed locally or remotely. To
execute these stored codes, the Oracle tools have their own PL/SQL engine
(independent of the engine present in the Oracle server). The engine first filters out
the SQL statements to send them individually to the SQL statement executor in the
Oracle server. It then processes the remaining procedural statements in the
procedural statement executor in the PL/SQL engine. The procedural statement
executor processes data, which is already inside the client environment and not in
the database. This reduces the workload on the Oracle server and also the amount of
memory required.

Performance Enhancements of Applications
When SQL statements are sent to the Oracle server one at a time, each statement
results in a call to the Oracle server, leading to performance overhead and network
traffic. If your application is SQL intensive, then instead of sending SQL statements
individually to the server, you can put them into one block using PL/SQL and send
the entire block to the server at one time. This reduces network traffic.

PL/SQL also operates with Oracle development tools, thereby adding procedural
processing power to these tools and enhancing performance.



Modularized Program Development
PL/SQL programs are made up of one or more blocks. These blocks may be
individual ones or may be nested within another. That is, a block may represent a
small part of another block, which may in turn be part of a whole unit of code. The
units (procedures, functions or anonymous blocks) making up a PL/SQL program are
called logical blocks.

A diagrammatic representation of modularization is:

The advantages associated with modularized development of programs are:

 Logical groupings of related statements within blocks
 Nesting blocks within larger blocks help build powerful programs
 Breaking down complex problems into manageable sets of logical, well-defined
modules, which can be implemented within blocks

Portability
PL/SQL is portable. That means, PL/SQL programs can be run wherever the Oracle
server exists. There is no need to tailor them to suit each new environment. This is
achieved because PL/SQL is native to the Oracle server, and therefore can be moved
to any environment (operating system or platform) that supports the Oracle server.

PL/SQL code can also be moved between the Oracle server and Oracle Developer
applications by writing programs and creating libraries in different environments.



Variable Declaration

In PL/SQL, you can declare variables:

 To use them in SQL and procedural statements
 Belonging to different data types
 Dynamically based on the structure of tables and columns in the database

Programming with Procedural Language Control Structures
PL/SQL allows the usage of control structures, which enable you to execute:

 Sequence of statements conditionally
 Sequence of statements iteratively in a loop
 Individually the rows returned by multiple-row query

Handling Errors
PL/SQL implements error handling functionality by:

 Processing Oracle server errors with error handling routines
 Declaring your own error conditions and process them with error handlers

PL/SQL Block Types and Constructs
There are two block types and different types of constructs in PL/SQL. A block is a
PL/SQL code. A construct is the way in which a block is written to implement
different functionality.

Block Types
Logical blocks are the basic units of code that make up a PL/SQL program. The two
kinds of PL/SQL blocks are:

 Anonymous blocks
 Named blocks or Subprograms

Anonymous Blocks
Anonymous blocks are declared at that point in an application from where they are
to be executed and are passed to the PL/SQL engine for execution at runtime. These
blocks are unnamed blocks. They can be embedded in the iSQL*Plus environment.
An application trigger consists of these blocks.

Subprograms
Unlike anonymous blocks, named blocks or subprograms are given a name. These
blocks can be invoked for execution and they can also accept parameters.



Subprograms can be declared as Procedures or Functions. You declare a subprogram
as a Procedure to perform an action, and you declare a subprogram as a Function to
compute a value. Subprograms can be written and stored either at the server side or
at the client side.

Constructs
There are various PL/SQL program constructs available that use the basic PL/SQL
block. The availability of program constructs depends on the environment in which
they are executed.

The different program constructs are given below.



PL/SQL Block Structure
To write a PL/SQL block, you need to know the different parts of a PL/SQL block and
what each part should hold. The structure of all PL/SQL blocks is the same. The only
difference is that, if it is an anonymous block it is not given a name.

A PL/SQL block has three sections . They are :

 Declarative section
 Executable section
 Exception handling section

The declarative section is where the variables and constants used in the body of the
block are declared. Any cursors or user-defined error handlers that are used in the
body are declared here. This section is optional.

The executable section holds the set of statements or the logic of the tasks that are
to be performed. You can include SQL statements to make changes to the database
and PL/SQL statements to manipulate data in the block. The statements in this block
are enclosed within the keywords BEGIN and END. This section is mandatory.

The last section of a block is the exception section. Here a set of statements is
written to handle any errors that might occur when the statements in the executable
section are being executed. This section is optional .



The diagramatic expression of PL/SQL block structure is given below.

The syntax for writing a PL/SQL block is:

DECLARE
<variable name> datatype(size);
BEGIN
SQL statements;
PL/SQL statements;

EXCEPTION
WHEN <exception name> THEN
…
END;
/
Some points that will help you write a block:

 A line of PL/SQL text which contains group of characters known as lexical
units. These units are classified as follows:

 Delimiters are simple or compound symbols that have a special meaning to
PL/SQL. The following table presents both the simple as well as the compound
symbols:



 Identifiers are used to name PL/SQL program constructs such as Constants,
Variables and Exceptions. The following points need to be kept in mind while
using identifiers:

• Identifiers can be up to 30 characters in length, but ensure they start
with an alphabet.

• Do not give the same name for the identifiers as the name of columns
in a table used in the block. If so, then the Oracle server assumes that
the table column is being referred.

• An identifier consists of a letter, followed (optional) by other letters,
numerals, underscores, dollar signs and number signs. The following
characters are however illegal:
Abc&efg – illegal ampersand
Abc-efg – illegal hyphen
Abc/efg – illegal slash
Abc efg – illegal space

• Identifiers should not be reserved words except when they are used
within double quotes, for instance “INSERT”.

 Literals are made up of definite values such as character, numeric, string or
Boolean values, not represented by identifiers. These are case sensitive.



Literals are of two types:

• Character literals: are all the printable characters such as letters,
numerals, spaces, and special symbols. Specify character literals in
single quotes.

• Numeric literals: are represented either by a simple value such as –12
or by a scientific notation such as 3E6.

Comments are extra information given by the programmer to improve
readability in a code, to enable
documenting in each phase and debugging.
PL/SQL code can be commented in two ways:
• Single line comment represented by --
• Multi line comment represented by /* */

 Use a semicolon (;) at the end of all SQL and PL/SQL control statements and
the
END keyword.
 Do not use semicolons after the keywords DECLARE, BEGIN and EXCEPTION.
 Increase the readability of the block by writing the keywords in uppercase.
 Use a slash (/) to terminate a PL/SQL block on a line by itself.

Using Quotes in Literals
Oracle 10g allows you to define your own string delimiters to remove the need to
double up any single quotes.

SET SERVEROUTPUT ON

BEGIN

--original code

DBMS_OUTPUT.PUT_LINE(‘He is New Jersey Library
‘’s Member!’);

-- using quote symbol

DBMS_OUTPUT.PUT_LINE(q’# He is New Jersey
Library‘s Member!#’);
DBMS_OUTPUT.PUT_LINE(q’[ He is New Jersey
Library‘s



Member !]’);

END;
/

He is New Jersey Library‘s Member!
He is New Jersey Library‘s Member!
He is New Jersey Library‘s Member !

PL/SQL procedure successfully completed

Operators in PL/SQL
The following operators are supported in PL/SQL:
 Arithmetic
 Logical
 Relational or Comparison
 Concatenation
 Exponentiation [Represented by (**)]

SQL Functions in PL/SQL Statements
All the SQL functions can also be used in procedural statements in a block.

These include:
 Single-row number and character functions
 Datatype conversion functions
 Date functions
 Timestamp functions
 GREATEST and LEAST functions

The functions that cannot be used in procedural statements are:

 DECODE
 Group functions like AVG, MIN, MAX, COUNT, SUM, STDDEV and
VARIANCE. These functions work only on a group of rows in a table and
hence, they can be used only with the SQL statements in a PL/SQL block.

Variables
A variable are named memory locations used to store data temporarily. The data
stored in variables is used in the blocks and then processed. When the processing is
completed, the data held in the variables may be written to the database or simply
erased in case of session wide variables.

Why is a Variable used?
A Variable stores data temporarily. It manipulates the stored data and performs
calculations with the data without accessing the database. Once declared, variables



can be used repeatedly in an application by referencing them in other statements in
the block.

When variables are declared using %TYPE and %ROWTYPE (more information is
provided later in the chapter), you are infact basing the variable declaration on the
column definition of a table. In this case, if the column definition changes, then the
variable declarations also changes accordingly. This helps in data independence,
reduces maintenance cost and allows the program to adjust to the new business
logic.

How to handle variables in PL/SQL?
In a PL/SQL block, variables are:

 Declared and initialized in the declarative section of the block.
 Assigned new values in the executable section. On doing so, the existing
value is replaced with the newly assigned value. Care must be taken to see
that a variable being referred to is already declared in the declarative section.
Forward references cannot be made.

Types of Variables
Variables are of two types. They are:

 PL/SQL variables
 Non-PL/SQL variables

PL/SQL Variables
PL/SQL variables have a data type that specifies a storage format, constraints and
also valid range of values.
The data types used to declare PL/SQL variables are:

 Scalar data types are those that correspond to database column types. These
data types hold only a single value. The base scalar data types include:

 CHAR
 VARCHAR2
 LONG
 LONG RAW
 NUMBER
 BINARY_INTEGER
 PLS_INTEGER
 BINARY_FLOAT
 BINARY_DOUBLE
 BOOLEAN
 DATE
 TIMESTAMP
 TIMESTAMP WITH TIMEZONE
 TIMESTAMP WITH LOCAL TIMEZONE
 INTERVAL YEAR TO MONTH
 INTERVAL DAY TO SECOND



Binary_Float and Binary_Double are the two new Datatypes introduced in
Oracle10g.They represent floating point numbers in IEEE 754 format (Institute of
Electrical and Electronic Engineers) and require 5 byte and 9 bytes to store the
values respectively. IEEE format s supported by most of the computer system
operating through native processor instructions thereby helping us to carry out
complex computations using floating point data.


 Composite data types are those that are defined by users. They enable you to
manipulate groups of data in PL/SQL blocks

 Reference data types are those that hold values pointing to other objects.
These are also known as pointers.

 LOB (large object) data types: are those that hold values, which specify the
location of large objects such as graphic images. These values are known as locators.
Large objects are stored in the same database as the table but not within the table.
LOB data type allows you to store unstructured data of a maximum of 8-128
terabytes. This data could be a movie clip or a graphic image or a sound wave form.
LOBs are further classified into:

 CLOB (Character Large Objects) is used to store large blocks of character
data of a single byte.
 BLOB (Binary Large Object) is used to store large binary objects within the
database.
 BFILE (Binary File) is used to store large binary objects that are in the
operating system files outside the database.
 NCLOB (National Language Character Large Objects), are used to store large
blocks of NCHAR data that may be single-byte or fixed-width multiple bytes

The syntax for declaring PL/SQL variables is:

identifier [CONSTANT] datatype [NOT NULL] [:= | DEFAULT expr];

Where,

identifier is the name assigned to the variable declared.

CONSTANT specifies a constraint that the value of the variable cannot change.
Constant variables must be initialized. While declaring a variable as a constant, the
CONSTANT keyword must precede the datatype specification.

DATATYPE specifies the type of data the variable can hold. It could be scalar,
composite, reference or LOB datatype.

NOT NULL specifies a constraint that the variable must contain a value. Therefore,
NOT NULL variables must be initialized.

:= is the assignment operator used to assign an expression to a variable. Instead of
the assignment operator, the DEFAULT expr (expression) can be used to assign
values to the variables.



By default, all variables are initialized to NULL. To prevent null values, variables are
initialized using the DEFAULT keyword.

The following code snippet shows how PL/SQL variables are declared in the
declarative section of a block:
DECLARE
FirstName CHAR(20);
BranchID CHAR(7) NOT NULL: = ‘09RANNJ’;
FeeAmt CONSTANT NUMBER(2): = 15;
CatgName CHAR(15) DEFAULT ‘Fiction’;

% TYPE Attribute
If you need to store a database column value in a variable or write a value from a
variable to a database column, then the data type of the variable needs to be the
same as that of the database column. You can use the %TYPE attribute to declare a
variable to be of the same data type as that of a previously declared variable or
database column.

Incorrect variable data types generate PL/SQL errors during execution. When you
want to declare a variable using a table attribute instead of the datatype the syntax
is

<variable_name> table.columnname%TYPE

For example, in case you want to declare a variable that will store the address of a
library member, you will write in the following syntax:

DECLARE
Address VARCHAR2(45);

But, the above declaration will result in an error when an attempt is made to
populate the variable with address details of members from the database table. This
is because there is a mismatch in type specification of the variable. The datatype
width of the vAddress column in table Member is 50, but you have declared it as
45. To overcome this, declare the variable using %TYPE attribute as follows:

DECLARE
Address Member.vAddress%TYPE;

This statement declares a variable whose datatype and width is based on the
vAddress column.

If you want to declare a variable of the same type as a previously declared variable
then the syntax is

<variable_name> variable_name%TYPE



Using %TYPE attribute to declare a variable based on a previously declared variable,
is illustrated in the section dealing with the iSQL*Plus variables within PL/SQL blocks.
Datatype and Variable size is determined when the block is compiled. So even if
there is a change in the database column datatype the code manages the changed
datatype information.

Data Conversion Functions
In any programming language generally, we have to deal with different datatypes
simultaneously or receive data which is not in the default format. In such cases,
Oracle server implicitly converts data into valid datatypes wherever feasible. Explicit
conversions come into the scenario where automatic conversions are not possible.

Oracle Server takes care of implicit conversion between
1. Character and Number
2. Character and Date

But how is it done? Let us take an example.

DECLARE
cons_nfine NUMBER(3):=50;
cons_extra_fine VARCHAR2(20):=’5';
tot_fine Transaction.nfine%TYPE;
BEGIN
tot_fine:= cons_nfine+cons_extra_fine;
DBMS_OUTPUT.PUT_LINE(‘The total fine payable is Rs.‘||
tot_fine);
END;
/

So, did you notice something?
Variable cons_nfine is of number datatype and cons_extra_fine is of VARCHAR2
datatype. While assigning the result to tot_fine variable, cons_extra_fine is
converted to number by PL/SQL executer and then the operation is performed.



To perform explicit conversion, following built in functions can be used.
to_char()
to_number()
to_date()
to_Binary_float()
to_Binary_double()

DECLARE
v_Date date:= to_Date( ‘April 04 2007’,’Month dd YYYY’);
BEGIN
DBMS_OUTPUT.PUT_LINE(‘You have entered ‘ ||v_Date ||’ as
input’);
END;
/

Example to show the usage of new datatypes.

DECLARE
l_binary_float BINARY_FLOAT;
l_binary_double BINARY_DOUBLE;
BEGIN
l_binary_float := 2.1f;
l_binary_double := 2.00001d;
DBMS_OUTPUT.PUT_LINE(l_binary_double);
DBMS_OUTPUT.PUT_LINE(l_binary_float);
l_binary_float := TO_BINARY_FLOAT(2.1);
l_binary_double := TO_BINARY_DOUBLE(2.00001);
DBMS_OUTPUT.PUT_LINE(l_binary_double);
DBMS_OUTPUT.PUT_LINE(l_binary_float);
END;
/



Non-PL/SQL Variables
Since PL/SQL has neither input nor output capabilities, it relies on the environment in
which it is executed in order to pass values into and out of a PL/SQL block.

The following non-PL/SQL variables can be used within PL/SQL blocks:

 Substitution variables
 Host variables

Substitution variables are those that you can use to pass values to a PL/SQL block at
runtime. To reference a substitution variable in a block, prefix it with an ampersand
(&). Before the block is executed the values for the variables are substituted with the
values passed.

Hence, you cannot input different values for the substitution variables using a loop.
The substitution variable can be replaced only by one value.
Here is an example showing the use of substitution variables within PL/SQL blocks.
Suppose, the library wants to calculate its quarterly income based on its annual
income. To do this, it declares a substitution variable, which would prompt the user
to enter the figure of annual income. Based on the value entered, the quarterly
income would be calculated.

DECLARE
AnnualIncome NUMBER (7): = &annualinc;
QuarterlyInc AnnualIncome%TYPE;
-—declaring variable based on previously declared variable
using --%TYPE attribute.
BEGIN
QuarterlyInc:= AnnualIncome/4;
DBMS_OUTPUT.PUT_LINE (‘The quarterly income of the library
is: ’|| QuarterlyInc);
END;
/

In the above block, to display the quarterly income calculated, you can specify the
DBMS_OUTPUT.PUT_LINE in the PL/SQL block. DBMS_OUTPUT is an Oracle supplied
package and PUT_LINE is a procedure within it. To use this you need to specify the
information you want printed, in parentheses, following the
DBMS_OUTPUT.PUT_LINE command as shown in the above code:

DBMS_OUTPUT.PUT_LINE (‘The quarterly income of the library
is: ’|| QuarterlyInc);

For DBMS_OUTPUT.PUT_LINE to work, you need to run the iSQL*Plus command
SET SERVEROUTPUT ON.

iSQL*Plus host variables (also known as bind variables) are used to pass runtime
values from the PL/SQL block back to the iSQL*Plus environment. These variables
can be referenced in a PL/SQL block by placing a colon(:) before the variable.



The keyword VARIABLE is used to declare a bind variable. The syntax is:

VARIABLE <variable_name> datatype

The syntax to display the variable value is:

PRINT <variable_name>

Bind variables cannot be referred within the PL/SQL block of a function, procedure or
a package.

In a PL/SQL block, to differentiate between host variables and declared PL/SQL
variables, prefix the former with a colon(:).

The code wherein you had calculated the quarterly income using substitution
variables can be re-written using host variables as follows:

VARIABLE QuarterlyInc NUMBER
DECLARE
AnnualIncome NUMBER(7):= &AnnInc;
BEGIN
:QuarterlyInc:= AnnualIncome/4;
END;
/
old 2: AnnualIncome NUMBER(7):= &AnnInc;
new 2: AnnualIncome NUMBER(7):= 80000;

PL/SQL procedure successfully completed.

PRINT QuarterlyInc

QUARTERLYINC
------------
20000

The above example shows the Host variable being assigned a value inside a PL/SQL
block. To assign a value to a host variable outside the Pl/SQL block following can be
done:-
SQL > VARIABLE QuarterlyInc NUMBER
SQL > Exec :QuarterlyInc := 20000
SQL> PRINT QuarterlyInc

QUARTERLYINC
------------
20000



Where,
Exec stand for Execute privilege.

Nested Blocks
PL/SQL allows blocks to be nested wherever you can have an executable statement.
[This makes the nested block a statement.] Hence, the executable part of a block
can be broken down into smaller blocks. Even the exception section can contain
nested blocks.

Variable Scope
Issues that concern references to identifiers can be resolved taking into account their
scope and visibility.
By scope, we mean that region of a program unit from which an identifier can be
referenced. For instance, a variable in the declarative section can be referenced from
the exception section of that block.

The diagram shown below illustrates the concept of nested blocks and variable
scope.

By
visibility,
we mean



the regions from which an identifier can be referenced without using a qualified
name.

The following code snippet shows how to qualify identifiers:

<<outer_blk>> --Block label
DECLARE --This is the parent block
JoiningDt DATE;
BEGIN
DECLARE --his is the child block
JoiningDt DATE;
BEGIN
…
outer_blk.JoiningDt :=TO_DATE (’20- JAN-1998’, ‘DD-MON-
YY’);
END;
…
END;
/

In the code snippet, a variable with the same name as the variable declared in the
outer block is declared in the inner block. To reference the outer block variable in the
inner block, the variable is qualified by prefixing it with the block name.
Identifiers are considered local to the PL/SQL block in which they are declared, and
are considered global to all its sub-blocks. Within the sub-block, only local identifiers
are visible because to reference the global identifiers you must use a qualified name.
If a block cannot find the identifier declared locally, it will look up to declarative
section of the enclosing block (parent block). However, the block will never look
down to the enclosed blocks (child blocks).

Look at the following code and determine the variable scope:

<<OUTER_BLK>>
DECLARE
vSal NUMBER(8,2) := 50000;
vComm NUMBER(8,2) := vSal * 0.10;
vNote VARCHAR2(200) := ‘Eligible for commission’;
BEGIN
DECLARE
vSal NUMBER(8,2) := 90000;
vComm NUMBER (4) := 0;
vAnnualComp NUMBER(8,2) := vSal + vComm;
BEGIN
vNote := ‘Manager not’||vNote;
OUTER_BLK.vComm := vSal * 0.20;
END;
vNote := ‘Salesman’||vNote;

END;



/

Based on the rules of scoping, determine values of:

 vNote at position 1
 vAnnualComp at position 2
 vComm at position 1
 OUTER_BLK.vComm at position 1
 vComm at position 2
 vNote at position 2

Guidelines for Writing PL/SQL Code
Programs can be indented using carriage return,tabs and aligning keywords in the
same line at different levels.Writing so, the task of debugging is made simpler.
While writing programs we can follow a case convention, though PL/SQL is not case
sensitive. For instance:-

• All keywords should be written in uppercase.
• They must be aligned in the same line.
• Table names and column names are to be in Initcap and lower case
respectively.

Indented programs improve the performance in those cases where similar
statements are to be issued repeatedly because there is no need to parse the
statements again.

Let us write a program following all the rules stated above.

DECLARE
AnnualIncome NUMBER(7):= 60000;
QuarterlyInc NUMBER(8,2);
BEGIN
QuarterlyInc:= AnnualIncome/4;
DBMS_OUTPUT.PUT_LINE(‘The Quarterly income is ‘||
QuarterlyInc);
END;

/

Here, the keywords are aligned in the same line but at different levels. This
improves readability of the code.



Summary

In this chapter, you have learnt that:

PL/SQL bridges gap between SQL and a procedural language.

 Two types of PL/SQL blocks are:
1. Anonymous or unnamed blocks which are not stored in database and
compiled each time they are executed.

2. Named Blocks which are compiled only once and stored in the database.

 The three sections of a PL/SQL Block are:
1. Declarative Section, where all the variables used in the program are
declared. This is optional. Keyword: DECLARE

2. Executable Section where actual logic of the program lies. Keyword:
BEGIN

3. Exception Section where all the errors are handled. This section is
optional. Keyword: EXCEPTION

4. END to end the PL/SQL program.

 PL/SQL variables are declared and are accessible only within that PL/SQL block.
Non- PL/SQL variables are declared outside the PL/SQL block and are available
throughout the session.

 Two new datatypes FLOAT and DOUBLE introduced in this release help users in
computing complex calculations.

 Nesting of blocks is allowed to have good control on the scope of the variables.
Nested Blocks can also have exception sections.



Lab Exercises
1. Identify whether the following declarations are correct or incorrect:

a) DECLARE
empID NUMBER(5);

b) DECLARE
str1, str2, str3 VARCHAR2(20);

c) DECLARE
hiredate DATE NOT NULL;

d) DECLARE
on BOOLEAN := 5;

2. Create an anonymous block to display the phrase “Welcome to the world of
PL/SQL”.

3. Create a block that declares two variables, one of VARCHAR2 type and the
other of NUMBER type. Assign the following values to the variables and display the
output on the screen.



4. Write a PL/SQL code to display the ID, Last Name, job ID and salary of an
employee?

5. Among the following which datatypes are enhancements of Oracle10g?

a) BINARY_INTEGER

b) BINARY_FLOAT

c) BINARY_DOUBLE

6. Display the following text using quote operator q:

I’m Oracle certified,you’re not.


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