MySQL ifNull vs isNull?

Question

What is the basic difference between IFNULL and ISNULL in MySQL, and how can they provide an optimized solution for handling null values? I have been using an IF condition every time, but I'm looking for a more efficient approach.

So what I want is to use functions depending on the needs in the project as writing everytime IF is not an optimized solution.

Answer 1

They server two completely different functions.

ISNULL(value) is a boolean operator that returns 1 or 0 depending on whether or not the value passed in is null. It can be used in if and case statements to determine logic flow. Example:

SELECT OrderID, 
CASE
    WHEN ISNULL(AmountDue) THEN "Paid in full"
    WHEN DATE(DueDate) < date(NOW()) THEN "Order is past due"
    ELSE CONCAT("Order is due on ", CONVERT(VARCHAR, DueDate, 121))
END
FROM OrderDetails;

IFNULL(value1, value2) is used to handle a situation where you want one value, unless it is null, in which case you want a second value. Example:

select IFNULL(MiddleName, "No Middle Name") from customers