My knowledge of SQL NULL is rusty, but I think NULL is just plain unordered with respect to other values, more akin to a NaN value in floating-point than an indeterminate value.
SQLite-3.54 in-memory-> select NULL < 0 or NULL == 0 or NULL > 0;
╭──────────────────────╮
│ NULL < 0 or NULL ... │
╞══════════════════════╡
│ NULL │
╰──────────────────────╯Though all of this explanation is only in LLVM IR level. In C, this is just UB and it is also possible that this will erase your hard drive.