How To Test NULL Values

Q

How To Test NULL Values? - Oracle DBA FAQ - Understanding PL/SQL Language Basics

✍: FYIcenter.com

A

There ate two special comparison operators you can use on NULL values:

  • "variable IS NULL" - Returns TRUE if the variable value is NULL.
  • "variable IS NOT NULL" - Return TRUE if the variable value is not NULL.

The following sample script shows you examples of comparing NULL values:

DECLARE
  next_task CHAR(80);
BEGIN
  next_task := NULL;

  IF next_task IS NOT NULL THEN
     DBMS_OUTPUT.PUT_LINE('I am busy.');
  ELSE
     DBMS_OUTPUT.PUT_LINE('I am free.');
  END IF;
  
  IF next_task IS NULL THEN
     NULL;
  ELSE
     DBMS_OUTPUT.PUT_LINE('... working on ' || next_task);
  END IF;
END;

Note that "variable = NULL" is not a valid operation. This script should print this:

I am free.

2007-04-29, 5091👍, 0💬