Question 186251 in Mysql Question posted in
The official MySQL documentation can be found here.

MySQL ifNull vs isNull?

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.

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3

Answers


  1. 0

    The basic difference between IFNULL and ISNULL in MySQL is as follows:

    IFNULL: IFNULL function is used to handle null values in a result set. It takes two arguments, the first argument is the value to check for null, and the second argument is the value to return if the first argument is null. If the first argument is not null, then it is returned as the result.

    ISNULL: ISNULL function is used to check if a value is null or not. It takes only one argument and returns a boolean value (1 or 0). If the argument is null, it returns 1 (true), indicating that the value is null. If the argument is not null, it returns 0 (false), indicating that the value is not null.

    The optimized solution depends on the specific use case. If you simply want to handle null values and replace them with a default value, IFNULL can be used. However, if you want to check if a value is null or not, ISNULL is more appropriate.

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  2. 0

    In MySQL, ISNULL simply checks if a value is null or not. IFNULL acts like COALESCE and will return the 2nd value if the first value is null.

    Are you perhaps mistaking ISNULL in SQL Server as the one in MySQL? In SQL Server ISNULL is the same as IFNULL in MySQL.

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  3. 0

    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
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