In the previous chapter, you learned how to compose SQL statements to query data from relational databases such as SQLite and MySQL. Is there a way to directly use SQL to query data frames in R as if these data frames are tables in relational databases? The sqldf package says yes.
This package takes advantage of SQLite, thanks to its lightweight structure and easiness to embed into an R session. Run the following command to install this package if you don't have it:
install.packages("sqldf")
First, let's attach the package, as shown in the following code:
library(sqldf) ## Loading required package: gsubfn ## Loading required package: proto ## Loading required package: RSQLite ## Loading required package: DBI
Note that when we attach sqldf, a number of other packages are automatically loaded. The sqldf package depends on these packages, because what it does is basically transferring data and converting data...
