If you want to suppress the unused level of Species, you can use factor() :

table(base$Species)
table(factor(base$Species))

2008/8/28 glaporta <glaporta@freeweb.org>

>
> Hi,
> sqldf is a fantastic package, but when the SELECT procedure runs unused
> levels remain in the output. I tried with the drop function, but without
> success. Do you have any suggestions?
> Thanx, Gianandrea
>
> data(iris)
> require(sqldf)
> base<-sqldf("select * from iris where Species <> 'setosa'")
> str(base) # Species with 3 levels!
>
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