Dear R experts,
I've realized that it might not be possible to define a negative SELCET
statement in a SQL call so now I'm looking for the smoothest way to generate a
list of what I would like from my large database by first pulling all the names
with a query like this "SELECT top 1 * FROM your_table" (thank you Bart Joosen
for the idea) and then subtract the variables I am not allow to pull manually
ending up with a 'positive' definition of what I want, something I can use in a
SQL SELCT statement (see my email on this list from yesterday for more on
that).
When I query the database for the variable names I get something similar to
'DBquery' in my working example below, but considerable longer with over 2400
hundred variables. As I only need to remove two or three variables I would like
to define a lookup table (like the list 'lookup' in my example) and subtract
that from my data base query. Now to my question. Is there a way I can subtract
one list from another? Like setoff or alike?
I would like to end up with a list like the one shown in my example called
'result.' In short, I would like to subtract 'lookup' from 'DBquery' and end up
with 'result,' please note that 'result' is a list fo vecktors and not a list
of dataframes. In my real life example DBquery is considerable longer so
defining that by hand would make a really really long syntax.
Hope someone know some smart function that I can use to solve my problem in an
elegant way.
Thanks for reading.
Erick
###### begin R code ######
DBquery <- list(tableA=data.frame(id = numeric(0), atwin = numeric(0),
atrout = numeric(0)),
tableB=data.frame(id = numeric(0), mq = numeric(0), z =
numeric(0), m = numeric(0)),
tableC=data.frame(V1 = numeric(0), mfn = numeric(0), iiff
= numeric(0)),
tableD=data.frame(id = numeric(0), msf = numeric(0),
oom = numeric(0)))
lookup <- list(tableA= c('atwin', 'atrout'),
tableB= c('m', 'z'),
tableC= 'ALL')
### ...
result <- list(tableA= c('id'),
tableB= c('id', 'mq'),
tableC= c('V1', 'mfn', 'iiff'))
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