[R] group by and merge two dataframes

[Massimo Bressan]

given this "bare bone" example:

df1 <- data.frame(id=rep(1:3,each=2), item=c(rep("A",2), rep("B",2), 
rep("C",2)))
df2 <- data.frame(id=c(1,2,3), who=c("tizio","caio","sempronio"))

I need to group the first dataframe "df1" by "id" and then merge with 
the second dataframe "df2" (again by "id")
so far I've manged to accomplish the task by something like the following...

# start

require(sqldf)
tmp<-sqldf("select * from df1 group by id")
merge(tmp, df2)

#end

now I'm wonderng if there is a more efficient and/or elegant way to 
perform it (also because in fact I'm dealing with much more "heavy" 
dataframes);

may be possible through a single sql statement?  or by using a different 
package functions (e.g. dplyr)?
my attempts towards these alternative approaches miserably failed ...

thanks