Why don't you check manually the datatypes of the columns those are present in the select list? That would be the simplest way to do this.
I don't think there is any direct way to know the datatype of the columns in the result. But you can find the datatype of columns a table by following query
SELECT Col.NAME [COL NAME],Typ.NAME [DATA TYPE]
FROM SYS.COLUMNS Col
INNER JOIN SYS.TYPES Typ ON Col.USER_TYPE_ID = Typ.USER_TYPE_ID
WHERE Col.OBJECT_ID = OBJECT_ID('YourTableName')
Hope, it helps :)