method = "name_class" does not work for character string dates

[ggrothendieck]

This does not return a Date class column:

sqldf("select '2000-01-31' a__Date", method = "name__class")

Try variations of this SO answer to generate examples:

http://stackoverflow.com/questions/34748100/using-apply-in-r-similar-to-how-its-used-in-sql-server/34750312#34750312