Filling missing values using COALESCE()

In the previous exercise, you used the ISNULL() function to replace the NULL values of a column with another value.

Now, you want to create a new column, location, that returns the values of the airport_city column, and in case it has NULL values, return the value of airport_state. Finally, if airport_state is also NULL, you want to return the string 'Unknown'.

To do it, you can use COALESCE(), that evaluates the arguments between parenthesis and returns the first argument that is not NULL.

This exercise is part of the course

Cleaning Data in SQL Server Databases

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Exercise instructions

Use COALESCE() to return the first non NULL value of airport_city, airport_state, or 'Unknown'.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

SELECT
airport_code,
airport_name,
-- Replace the missing values
___(___, ___, '___') AS location
FROM airports

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