What is the difference between IS NULL and =NULL?

[colap]

What is the difference between IS NULL and =NULL?

SELECT * FROM user,course WHERE user.course is NULL;



SELECT * FROM user,course WHERE user.course=NULL;

Tables information is here: http://www.sitepoint.com/understanding-sql-joins-mysql-database/

[requinix]

IS NULL is how you check whether a value is actually NULL or not. You will get true/1 or false/0.

 

= NULL is normal comparison, except when you compare something with NULL you will simply get NULL as the result.

 

Try it:

SELECT 1 IS NULL;
SELECT 0 IS NULL;
SELECT NULL IS NULL;

SELECT 1 = NULL;
SELECT 0 = NULL;
SELECT NULL = NULL;

Edited August 18, 2015 by requinix