Which function retrieves a non-null value from a list, returning the first non-null entry?

The function that retrieves a non-null value from a list, returning the first non-null entry, is the COALESCE function. This function evaluates its arguments in order and returns the first one that is not null. This behavior is particularly useful when dealing with multiple potential sources of data, as it allows you to specify fallback options seamlessly.

For instance, if you are querying a database where a particular column can have null values, COALESCE can help you prioritize which value to display from a set of columns, ensuring that you always return useful data. This makes it essential for data processing and reporting, as you can avoid null values that might disrupt the flow of analysis or user experience.

The other functions listed serve different purposes. NULLIF, for example, checks two expressions and returns null if they are equal; otherwise, it returns the first expression. ISNULL checks whether a specific value is null and returns a specified replacement if it is. VALUE is not a standard SQL function focused on retrieving non-null entries. Therefore, COALESCE stands out as the correct choice for this requirement.