MySQL: Explain IFNULL() in MySQL.

 

In MySQL, the IFNULL() function is used to handle NULL values in expressions. It returns the first non-NULL expression among its arguments. If all the arguments are NULL, it returns NULL.

The basic syntax of IFNULL() is as follows:

sql
IFNULL(expr1, expr2)

Here, expr1 is the expression that you want to check for NULL, and expr2 is the value to be returned if expr1 is NULL.

For example:

sql
SELECT IFNULL(column_name, 'Default_Value') AS result
FROM your_table;

In this example, if the value in column_name is not NULL, it will be returned. If it is NULL, the string 'Default_Value' will be returned instead.

Another common use case is in the context of providing default values in SELECT statements or when working with calculations where NULL might cause issues.

sql
SELECT column1, column2, IFNULL(column3, 0) AS column3_with_default
FROM your_table;

In this example, if column3 is NULL, the IFNULL() function will replace it with the value 0.

It's important to note that while IFNULL() is commonly used, there is an equivalent function called COALESCE() in MySQL, which can handle more than two expressions. The syntax for COALESCE() is:

sql
COALESCE(expr1, expr2, ...)

Both IFNULL() and COALESCE() are handy for dealing with NULL values and providing default values or fallbacks in your queries.