MySql replace NULL values with empty string without effecting Rowset

Question: What is NULL Value in MySQL?
NULL values means don't have any value. It is neither empty NOR it have any value.

Question: Give an Example which is give NULL Values in Query?
NULL values means don't have any value. It is neither empty NOR it have any values.

SELECT u.id, u.first_name,u.last_name,b.address1 FROM `users` as u LEFT JOIN billings as b on b.user_id=u.id order by u.id desc limit 5;

See Screenshot below:

Give an Example which is give NULL Values in Query

Question: How we can replace the null value with empty string?
We can use mysql IFNULL function to replace the null values with empty string. See Example:

SELECT IFNULL(null,"") as value

Question: Give an Example to replace the NULL with empty string in mysql query?
We can use mysql IFNULL function to replace the null values with empty string. See Example:

SELECT u.id, u.first_name,u.last_name,IFNULL(b.address1,"") AS address1 FROM `users` as u LEFT JOIN billings as b on b.user_id=u.id  order by u.id desc limit 5;

See Screenhot below: