Very few SQL implementations have unsigned integers (I think only MySQL+MariaDB has it out-of-the-box?). From my conversations with the MS SQL Server dev team, other than the overall lack-of-demand, it’s because ISO SQL leans very heavily on implicit conversions, and implicit conversions between signed and unsigned types are a massive pain to implement and gracefully handle all edge-cases and in a way that doesn’t behave too unexpectedly (and remember that most SQL language users are likely unfamiliar with all the gotchas of C-style unsigned integers: most SQL users are business analysts, not low-level systems programmers). Besides, if you just want to disallow negative values then just use a CHECK constraint.

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Also, in general, it’s not enough to just add loads of distinct numeric types to a language or library; in fact that’s probably the wrong thing to do as it burdens the programmer with having to make (often hair-splitting) decisions ahead-of-time - instead I’d like the language to have me set-up high-level constraints/invariants on a numeric parameter, local, or field and then the compiler chooses the best low-level implementation based on those constraints (and constraint-inference a-la Hindley–Milner would be nice too)