IMHO categorical data model (https://www.categoricaldata.net/ https://www.categoricaldata.net/) has much better support for sum types than relational model (as

IMHO categorical data model (https://www.categoricaldata.net/ https://www.categoricaldata.net/) has much better support for sum types than relational model (as well as other advantages, roughly along the lines why to prefer type theory to set theory in math foundations), unfortunately practical databases and query languages are not yet well developed for it.