On Mon, Aug 20, 2012 at 7:27 AM, cindy.dol <cindy.dolom...@insa-lyon.fr> wrote:
> I use sqldf to join 2 dataframes from 2 distinct databases : a and b come
> from old sqldf's.
>
> sqldf("select a.*, b.*, case a.QTY when null then b.QTY else a.QTY end as
> NEW_QTY"
> from a inner join b on a.OBJECT=b.OBJECT")
>
> R doesn't understand "when null". I tried with "when NA", "when '' ", "when
> ' ' " but it doesn't work.
>
What does Oracle have to do with all this? Since its not clear what
your set up is here is a reproducible example along the lines of your
sql statement. BOD is a six row, two column data frame that comes
with R. We insert some NAs into two replicas of it:
> library(sqldf)
>
> # test data
> BODa <- BODb <- BOD
> BODa[1, 2] <- BODb[2, 2] <- NA
>
> sqldf("select Time, case when a.demand is null then b.demand else a.demand
> end as demand from BODa a join BODb b using(Time)")
Time demand
1 1 8.3
2 2 10.3
3 3 19.0
4 4 16.0
5 5 15.6
6 7 19.8
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