The SQL return type of any SQL function may be accessed, typically for
debugging purposes, by referring to the :attr:`_functions.Function.type`
-attribute::
+attribute; this will be pre-configured for a **select few** of extremely
+common SQL functions, but for most SQL functions is the "null" datatype
+if not otherwise specified::
+ >>> # pre-configured SQL function (only a few dozen of these)
>>> func.now().type
DateTime()
+ >>> # arbitrary SQL function (all other SQL functions)
+ >>> func.run_some_calculation().type
+ NullType()
+
These SQL return types are significant when making
use of the function expression in the context of a larger expression; that is,
math operators will work better when the datatype of the expression is