PL/SQL Comments

PL/SQL is a Procedural Language for SQL language that extends the functionality of the SQL within Oracle Database Management System. Comments can be used to make code more human-readable. It is a kind of note that programmers usually add while writing the code. In this article, We will learn about Comments in detail along with the types and benefits of using Comments.

Comments in PL/SQL

The comment makes the code more easy to read and understand. these statements we write as comments are not executed by the compiler and simply get ignored while executing the code. For example, suppose you are writing a PL/SQL block for Manipulating data in the database but the queries you are writing are way too complex for to understand others, hence in this case we can specify the comments wherever needed to make queries more readable and understandable by ourselves or by other programmers.

In databases sometimes we require some context about the query. To specify that context we use comments. In databases, comments are non-executable text that is inserted along with the query. We can specify comments while creating the following:

• Procedures in PL/SQL
• Views in DB
• Functions in PL/SQL
• Triggers in PL/SQL

Like most programming languages, we can also write comments in PL/SQL. There are two types of comments in PL/SQL:

1. Single-line Comments
2. Multi-line Comments

Comments in PL/SQL

Single-Line Comments

A Single line comment starts with the (–) double hyphen. It will affect the whole line (till end of line). We don’t need to specify the end.

Syntax of Single-Line PL/SQL Comment

-- This is a single line comment

Example 01: PL/SQL Program to illustrate Single-Line Comment

-- Here is a program for addition of two numbers in PL/SQL
DELIMITER //

CREATE PROCEDURE add_two_numbers()
BEGIN
  -- Declare variables a, b, and c of datatype INT
  DECLARE a INT;
  DECLARE b INT;
  DECLARE c INT;

  -- Assign value to variable a
  SET a := 10;

  -- Assign value to variable b
  SET b := 20;

  -- Performing addition of a and b and storing it into c
  SET c := a + b;

  -- Printing the result
  SELECT CONCAT('Sum is ', c) AS result;
END //

DELIMITER ;

Output:

Output after executing procedure

Explanation: As we can see after calling the procedure named add_two_numbers, all the comments are ignored by the compiler and the result of addition is returned.

Multi-Line Comments

Instead of commenting single line, we could also set of consecutive lines at ones using multi-line comments in PL/SQL. Multi-line comment in PL/SQL starts with a forward slash and asterisk (/*) and ends with an asterisk and forward slash (*/). Text or code between /* and */ will get ignored by the compiler.

Syntax of Multi-Line PL/SQL Comment

/* Multi line comment starts
. . .  continue . . .
. . .  continue . . .
. . .  continue . . .
Multi line comment ends */

Example 02: PL/SQL Program to illustrate the Multi-Line Comment

/* demonstrate the use of IN parameter in PL/SQL */
delimiter //

CREATE PROCEDURE inProcedure(IN param INT)
BEGIN

/* 
using the IN parameter in procedure 
adding the 5 to parameter and then printing the result
*/

select param + 5 as result;
END //

DELIMITER ;

Output:

Result after calling procedure inProcedure(23)

Explanation: Here, we have called the inProcedure(), with passing 23 as a parameter. program is adding 5 to 23 and we are getting results as 28. The Point to note here is that we have used multi-line comments to explain the program.

Benefits of Using Comments

• Comments make your code easy to read and understand.
• Comments play a crucial role while debugging, They assist you by easily understanding the logic behind the code.
• Comments provide ways to document your code by explaining the use of variables,and functions.
• Commenting can be used to mark future improvements.
• Commenting is used in documenting the code. especially in Version control systems.

Conclusion

Overall, Commenting in PL/SQL is a practice that aligns principles of good software engineering. By investing time in commenting developers can make the code base more readable. In general, it makes easier for the person to understand the code part with the help of Comment.