Instruction
Perfect! One more exercise!
Exercise
Show the sum of the total_cost for each department and year, and the total sum of total_cost for each year. Do not show the grand total.
Show the following columns: department, year, and the sum of total_cost (as total). Instead of NULLs in the department column, show the following text: 'unknown'.
Make sure that your table consists of the following columns: department, year, and total.



