How to check if field is null or empty mysql?

Either use

SELECT IF(field1 IS NULL or field1 = '', 'empty', field1) as field1 
from tablename

or

SELECT CASE WHEN field1 IS NULL OR field1 = '' 
       THEN 'empty' 
       ELSE field1 END AS field1
FROM tablename

If you only want to check for null and not for empty strings then you can also use ifnull as you tried. But that is not suitable for empty strings too.