Difference between sqldf and rmysql?

Question

sqldf and RMySQL are both R packages that allow access to a MySQL database (the former using the latter). They both allow statements like this:

RMySQL: "Run an arbitrary SQL statement and extract all its output (returns a data.frame):"

dbGetQuery(con, "select count(*) from a_table")
dbGetQuery(con, "select * from a_table") 

sqldf:

library(sqldf)
sqldf("select * from iris limit 5")
sqldf("select count(*) from iris")
sqldf("select Species, count(*) from iris group by Species")
# create a data frame
DF <- data.frame(a = 1:5, b = letters[1:5])

So what are the differences? What does sqldf offer that RMySQL doesn't?

Answer 1

sqldf is used to issue SQL statements, and have them act on data frames. iris is not a database table, but a built-in data set.

> head(iris, n=3)
  Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1          5.1         3.5          1.4         0.2  setosa
2          4.9         3.0          1.4         0.2  setosa
3          4.7         3.2          1.3         0.2  setosa

sqldf is not used to connect to databases.

Answer 2

Besides the observation by Lundberg that dataframes are acceptable targets for SQL-commands, there is also the point that sqldf can go against any (disk-resident) table in SQLite (the default), H2, MySQL, or postgresSQL: https://code.google.com/p/sqldf/