If you want to be able to write practically anything on mobile, including ≠, ≈, ‰, ℝ etc., have a look at Unexpected keyboard. No spellcheck or autocomplete, though.

I was on mobile so I didn't have a .XCompose available to type.

I feel the opposite. On mobile I have much easier access to special characters. I just need to hold down characters to get more variants.

SQL is definitely a programming language. Most dialects are Turing-complete in some way. Some allow custom functions and stored procedures.