(1) For the section size, do we have to show those sections that are empty?

(2) If empty sections were included, what would be the appropriate value for empty section – 0 or null (no record)? It seems that zero may affect the further calculations.

cysun wrote:

I think 4.20 is quite difficult as is, so let's not worry about empty sections.

If you do want to include empty sections, use outer join and then the function coalesce() to convert NULL to 0.

Thank you.

Empty sections (with corresponding 0's) could be also included into the result by using left join (no additional functions required).