I suspect that rather than injecting into one of the existing tables inside /etc/pihole/pihole-FTL.db that it may be better to create a new table then get Core DNS to write to that (date time, domain queried , local IP etc etc ) then do a union to get the stats back.
Of course its (relatively) early morning after a night out and I haven't drunk my coffee yet and I may be talking tosh.
Thinking further out loud you would probably end up needing to write a custom stats page as well ., or just export for analysis in excel