> A naive use of a UUID, which might look like 70E2E8DE-500E-4630-B3CB-166131D35C21, would be to treat as a string, e.g. varchar(36) — don’t do that!! “Oh, pshaw”, you say, “no one would ever do such a thing.”

> Think twice — in two cases of very large databases I have inherited at relatively large companies, this was exactly the implementation. Aside from the 9x cost in size, strings don’t sort as fast as numbers because they rely on collation rules.

Eh, I've done that before because it made some interaction with Entity Framework easier (don't recall what now). Hasn't really mattered. The space for storing GUIDs has never been a meaningful constraint for anything I've ever worked on (9x is also nuts and assumes that your database uses 4 bytes per character). Sorting UUIDs is also generally uninteresting since they aren't meaningful by themselves. Maybe if you're doing lots of joins you might care about this.