Spreadsheet-free answers
"Which category has the most dishes?" "Top 3 visitors?" — chains of cut, sort and uniq -c answer these in one line, on files far too big for a spreadsheet.
The classic pipeline
cut -d, -f1,3 menu.csv | head -4 tail -n +2 menu.csv | cut -d, -f2 | sort | uniq -c | sort -rn tail -n +2 menu.csv | sort -t, -k3 -n | head -3 tail -n +2 menu.csv | cut -d, -f1 | tr a-z A-Z | head -3 echo "a,b,,c" | tr -s , tail -n +2 menu.csv | cut -d, -f2 | sort -u