MySQL comparison with null value

In MySQL, NULL is considered as a 'missing, unknown value', as opposed to no value. Take a look at this MySQL Reference on NULL.

Any arithmetic comparison with NULL does not return true or false, but returns NULL instead., So, NULL != 'C' returns NULL, as opposed to returning true.

Any arithmetic comparison with 'NULL' will return false. To check this in SQL:

SELECT IF(NULL=123,'true','false') 

To check NULL values we need to use IS NULL & IS NOT NULL operator.

Based on my tests and the documentation here: http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html

You can compare null and get a boolean result using <=>
NOTE: it looks like NOT EQ operator, but it's EQ operator

For example:

select x <=> y; 
or
select @x <=> @y;

This also compares string vs null, string vs string, etc.