PL/SQL Hello World Program (Example)

In this tutorial, we will introduce SQL*Plus and learn how to connect it to the database.

After connection, we are also going to see how to write our first program, “Hello World”, in PL/SQL.

What is SQL*Plus?

SQL*Plus is an interactive and batch query tool that is installed with every Oracle installation. It can be found at Start > Programs > Oracle-OraHomeName > Application Development > SQL Plus. Alternatively, you can also download it from the Oracle Technology Network (OTN).

It has a command-line user interface, a Windows GUI, and a web-based user interface.

It allows the user to connect to the database and execute PL/SQL commands.

Connecting to Database

In this section, we are going to learn how to connect to SQL*Plus in the Windows GUI. When we open SQL*Plus, it will prompt for the connection details as shown below.

Connection Details

• Username: <user name of the database>
• Password: <password for that user>
• Host String: <host details along with the port number and SID of the database>

• After the successful connection, the SQL Plus will appear as shown below.

• We need to execute “set serveroutput on” if we need to see the output of the code.
• Now we are ready to work with the SQL*Plus tool.

How to write a simple program using PL/SQL

In this section, we are going to write a simple program for printing “Hello World” using an “Anonymous block“.

BEGIN
dbms_output.put_line ('Hello World..');
END;
/

Output:

Hello World...

Code Explanation:

• Code line 2: Prints the message “Hello World…”.
• The below screenshot explains how to enter the code in SQL*Plus.

Note: A block should always be followed by ‘/’, which sends the information to the compiler about the end of the block. Until the compiler encounters ‘/’, it will not consider the block complete, and it will not execute it.

Declaring and usage of variables in the program

Here we are going to print “Hello World” using variables.

DECLARE
text VARCHAR2(25);
BEGIN
text := 'Hello World';
dbms_output.put_line (text);
END;
/

Output:

Hello World

Code Explanation:

• Code line 2: Declaring a variable “text” of a VARCHAR2 type with size 25.
• Code line 4: Assigning the value “Hello World” to the variable “text”.
• Code line 5: Printing the value of the variable “text”.

Comments in PL/SQL

Commenting code simply instructs the compiler to ignore that particular code from executing.

Comments can be used in the program to increase the readability of the program. In PL/SQL, code can be commented in two ways:

• Using ‘–‘ at the beginning of the line to comment that particular line.
• Using ‘/*……*/’ we can comment multiple lines. The symbol ‘/*’ marks the start of the comment and the symbol ‘*/’ marks the end of the comment. The code between these two symbols will be treated as comments by the compiler.

Example: In this example, we are going to print ‘Hello World’ and we are also going to see how the commented lines behave in the code.

BEGIN
--single line comment
dbms_output.put_line ('Hello World');
/*Multi line commenting begins
Multi line commenting ends */
END;
/

Output:

Hello World

Code Explanation:

• Code line 2: Single-line comment, and the compiler ignored this line from execution.
• Code line 3: Printing the value “Hello World”.
• Code line 4: Multiline commenting starts with ‘/*’.
• Code line 5: Multiline commenting ends with ‘*/’.

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