John Cook looks at a querying language based on category theory:
My interest in category theory waxes and wanes, and just as it was was at its thinnest crescent phase I ran across CQL, categorical query language. I haven’t had time to look very far into it, but it seems promising. The site’s modest prose relative to the revolutionary rhetoric of some category enthusiasts makes me have more confidence that the authors may be on to something useful.
I’m going through some lectures on category theory now and am in a big functional programming phase, so this is interesting but I won’t be giving up SQL anytime soon for it.