Right... Good call. In that case, the sales table should have a default for the department id field set to 0, and then the unknown row would have an ID of 0

Because id cannot be null in table departments (cause PK), then no values will be provided for result.

If the db is built properly, the departments table would have a null row that would have the name "Unknown"

sugerencia,no es recomendable usar *, en el order by para que sea mas eficiente usar la posicion y no el nombre del campo.

Suggestion,
it is not advisable to use *,
use the position and not the name of the field in "order by" to make it more efficient.

Thanks, I hope I understood you correctly :)