SQL: [Docs] Check and improve null/edge-case arg handling from functions #68531
Description
Seems that currently we don't have consistency in the SQL function documentation regarding the case of nulls passed in as arguments. It would be nice to revisit the functions and have a common way of documenting this case and maybe other common behaviour for edge-case args. We can also consider stating the common behaviour for a group of functions (e.g. String functions) at a central place to avoid repeating it on each one of them.