Oracle PL/SQL Tutorial - PL/SQL Comments

• « Previous
• Next »

The PL/SQL compiler ignores comments.

Adding comments to your program makes the code more readable.

Typically, we use comments to describe the purpose and use of each code segment.

We can disable pieces of code by turning them into comments.

Single-Line Comments

A single-line comment begins with --.

It can appear anywhere on a line.

It extends to the end of the line.

The following code shows how to add comments to code block.

DECLARE -- w  w w .  ja  v  a  2 s  .com
  n_count     NUMBER; 
  num_tables  NUMBER; 
BEGIN 
  -- Begin processing 
  SELECT COUNT(*) INTO n_count 
    FROM USER_OBJECTS 
      WHERE OBJECT_TYPE = 'TABLE'; -- Check number of tables 
  num_tables := n_count;          -- Compute some other value 
  DBMS_OUTPUT.PUT_LINE('num_tables: ' || num_tables); 
  
END; 
/ 

The code above generates the following result.

The following code shows how to disable a delete statement.

DECLARE 
  n_count     NUMBER; 
  num_tables  NUMBER; 
BEGIN 
   -- DELETE FROM employees WHERE comm_pct IS NULL 
END; 
/ 

Multiline Comments

A multiline comments begins with /*, ends with */, and can span multiple lines.

We can use multiline comment delimiters to comment out sections of code.

DECLARE -- from  ww  w . j ava 2 s.  c o m
   n_pi              NUMBER := 3.14; 
   n_radius          NUMBER := 5; 
   n_area            NUMBER; 
BEGIN 
   /* this is a comment
   this is a comment. */ 
   n_area := n_pi * n_radius**2; 
   DBMS_OUTPUT.PUT_LINE('The n_area is: ' || TO_CHAR(n_area)); 
END; 
/ 

The code above generates the following result.

• Next »
• « Previous