What makes you say it's less efficient? It's exactly analogous to storing increasing decimal values between 0 and 1, just using base 26 digits (encoded A-Z) rat

What makes you say it's less efficient? It's exactly analogous to storing increasing decimal values between 0 and 1, just using base 26 digits (encoded A-Z) rather than base 10 or base 2. Start with .M (encoded as "M"); add in .F, .T to insert before or after. Once you find yourself trying to insert between .M and .N, do it by adding .MM. But in a database char types can be arbitrarily long, and database indexes are well suited to indexing them. That gives them a lot of advantages for this kind of usecase.