Nice! You can also use COALESCE with other functions: concatenation, multiplication etc. Take a look:
COALESCE(category, '') || ':' || COALESCE(type, '')
In the above fragment, a NULL category or type will be replaced by an empty string. Thanks to this, we can still see the type when the category is NULL and vice versa.
Show the following sentence: Product X is made in Y. Where X is the name and Y is the production_area. If the name is not provided, write 'unknown name' instead. If the production_area is not provided, write 'unknown area'. Name the column sentence.
Use the concatenation symbol || to create the right sentence. Remember about the period (.) at the end of the sentence.
