Достаточно взглянуть на источники пакета RODBC.
# from R/TypeInfo.R:
typesR2DBMS <-
list(MySQL = list(double="double", integer="integer",
character="varchar(255)", logical="varchar(5)"),
ACCESS = list(double="DOUBLE", integer="INTEGER",
character="VARCHAR(255)", logical="varchar(5)"),
# etc ...