Some system functions that have no parameters should not be passed with empty parentheses i.e. FUNCTION(). They should instead by passed without parentheses. Provide an option so that the parentheses are included as this may be required on particular database systems. By default, if no arguments are supplied then the parentheses should not be included.
Add property to SQLFunctionExpression called IncludeParenthesesWhenArgumentsEmpty which is false by default.