
Wishlist for sqldf package

- verbose argument

- MySQL

- H2


These depend on software outside of sqldf:

- MySQL (and H2?) support sign(), var_pop(), variance(), var_samp(), std() and 
  stddev_samp() functions but SQLite does not.

- neither MySQL nor SQLite supports median() or quantile()

- support quotes in csv files - H2?

- if database driver not specified through argument or option then
  MySQL is used if RMySQL package is loaded and SQLite is used otherwise.
  This is a bit fragile and it would be better if we could check that
  the MySQL driver (rather than package) had actually been loaded.  Note 
  that currently there is no way to check this but if RMySQL and DBI were 
  upgraded to support such discovery this feature could be added.

- there has been some talk about removing the automatic dot to undescore 
  conversion in the DBI layer that underlies both RSQLite and RMySQL.  If
  that were to be done then sqldf would have to be modified accordingly.

- improve class assignment heuristic.  If two input column names match an
  output name if they have different class then use raw for that column.
  Also if converting to factor check that levels is correct.

