sqldf is installed like any other R package using this command from within R:

	install.packages("sqldf")

This will download and install sqldf and all its dependencies including the
RSQLite driver which includes SQLite itself so its particularly simple to
install if you use sqlite.  (More info later on how to use one of the other
supported databases.)

sqldf can use one of 4 database systems:

	- sqlite via RSQLite driver R package (which includes sqlite itself)
	- H2 via RH2 driver R package (which includes H2 itself)
	- PostgreSQL via the RpostgreSQL driver R package or the RpgSQL driver
	- MySQL via the RMySQL driver R package


EXAMPLE OF INSTALLING AND USING WITH SQLITE

As SQLite itself is included right in the RSQLite driver and since sqldf
automatically installs RSQLite this is the easiest to install.  Just install
sqldf and there is nothing else to do:

	install.packages("sqldf")

	library(sqldf)

	# now we can use it with sqlite, e.g.
	sqldf("select * from iris limit 3")
	DF <- data.frame(a = 1:3, b = 4:6)
	sqldf("select * from DF")


EXAMPLE OF INSTALLING AND USING WITH RH2

H2 is the next easiest to install because, like sqlite, its an embedded database
that is included right in its R driver package.  You only need to install 
sqldf, java and RH2.

	# install java runtime
	install.packages("sqldf")
	install.packages("RH2")

	library(RH2)
	library(sqldf)

	# now we can use it with H2, e.g.
	sqldf("select * from iris limit 3")
	DF <- data.frame(a = 1:3, b = 4:6)
	sqldf("select * from DF")

EXAMPLE OF INSTALLING AND USING WITH RPOSTGRESQL

First install PostgreSQL.  

The R driver, RPostgreSQL, has no special installation instructions:

	install.packages("sqldf")
	install.packages("RPostgreSQL")

	library(RPostgreSQL)
	library(sqldf)

	# now we can use it with PostgreSQL, e.g.

	sqldf("select * from iris limit 3")
	DF <- data.frame(a = 1:3, b = 4:6)
	# careful! Postgres translates everything not quoted to lower case
	sqldf('select * from "DF"')

MYSQL

To use MySQL, it must be installed separately and RMySQL must be built
by the user making it a bit more difficult to install than others.

MORE INFO

There is installation info on the other databases on their CRAN web pages. See
the Installation Info links on these pages:

  http://cran.r-project.org/package=RH2 
  http://cran.r-project.org/package=RPostgreSQL
  http://cran.r-project.org/package=RpgSQL
  http://cran.r-project.org/package=RMySQL


RUNNING

If RH2, RpgSQL or RMySQL is loaded, e.g. library(RH2), then sqldf will notice 
it and use that database so there is nothing to specify.  

The following is typically unnecessary but if you have multiple database
drivers loaded and wish to explicitly specify one of them then use the
drv=... argument of each sqldf call or set options(sqldf.driver=...) in R.
The possible values of ... are "SQLite", "MySQL", "h2" or "pgSQL".

See FAQ #7 on the sqldf home page (http://sqldf.googlecode.com) for more.


PROBLEMS

sqldf uses gsubfn which can optionally use the R tcltk package but can also
run without that package substituting R code for it.  On Windows and most
other R installations, tcltk comes with the core of R and so you automatically
get it.  If the tcltk is package not present it will be automatically detected 
and it will automatically switch to R code.  

There have been reports of bad R builds in which R reports that it has tcltk
capability even though its missing. In that case you will get an error message
about tcltk being missing.  To address this issue its easiest to just run this
command to force it to use R code in place of tcltk:

	options(gsubfn.engine = "R")

See FAQ #5 on the sqldf home page (http://sqldf.googlecode.com) for more.


MORE INFO

There is more information on sqldf on the sqldf home page:

	http://sqldf.googlecode.com

Note the TROUBLESHOOTING, FAQs and EXAMPLES sections there.

There is also information in the help files:

    library(help = sqldf)
    ?sqldf
    ?read.csv.sql