Question

​Which of the following functions allows for different options, depending upon whether a NULL value exists?

A) ISNULL
B) COALESCE
C) NULLIF
D) IFNULL

Answer 1

The function that provides different options depending on the existence of a NULL value is IFNULL. It returns the first argument if it's not NULL; otherwise, it returns the second argument. COALESCE is similar but works with more than two arguments.

Step-by-step explanation:

The function that allows for different options depending upon whether a NULL value exists is the IFNULL function. This function takes two arguments; if the first is not NULL, it returns the first argument, otherwise, it returns the second argument. The COALESCE function is similar as it returns the first non-NULL value from a list of arguments. However, IFNULL specifically handles two options based on the presence of a NULL value.

Let's look at some examples:

• IFNULL(NULL, 'default_value') will return 'default_value' because the first argument is NULL.
• IFNULL('actual_value', 'default_value') will return 'actual_value' as the first argument is not NULL.

The other functions like ISNULL and NULLIF have different use cases. ISNULL replaces NULL with a specified replacement value, and NULLIF returns NULL if the two arguments are equal, otherwise, it returns the first argument.