Add support for some basic / popular functions :
string: LENGTH(), SUBSTRING(), UPPER(), LOWER()
CONCAT(), CONCAT_WS(), REPLACE(), STRPOS()
MD5(), sha.., hash…
BASE64(), binary… ascii… hex…
numeric: ABS(), CEIL(), FLOOR(), ROUND(), MOD()
date: NOW(), current-date(), current-date-time()
or CURRENT_DATE(), CURRENT_TIME()
EXTRACT()
use math-operators for sum, substraction?
conditional: CASE, IF(), NULLIF()
array: IN()