I have an SQLite database connection to a database file. I want to extract some data from one of the tables, do some processing in R and then create a temporary table on the same connection from the processed data. It needs to be a temp table because users may not have write access to the database, but I want to be able to query this new data alongside the data already in the database.
so, for example:
require(sqldf)
db <- dbConnect(SQLite(), "tempdb")
dbWriteTable(db, "iris", iris)
# do some processing in R:
d <- dbGetQuery(db, "SELECT Petal_Length, Petal_Width FROM iris;")
names(d) <- c("length_2", "width_2")
d <- exp(d)
and then I want to make a temporary table in the connection db
from d
I know I could do:
dbWriteTable(conn=db, name= "iris_proc", value = d)
but I need it in a temp table and there doesn't seem to be an option for this in dbWriteTable
.
One workaround I thought of was to add a temp table and then add columns and update them:
dbGetQuery(db, "CREATE TEMP TABLE iris_proc AS SELECT Species FROM iris;")
dbGetQuery(db, "ALTER TABLE iris_proc ADD COLUMN length_2;")
But then I can't get the data from d
into the columns:
dbGetQuery(db, paste("UPDATE iris2 SET length_2 =", paste(d$length_2, collapse = ", "), ";"))
Error in sqliteExecStatement(con, statement, bind.data) :
RS-DBI driver: (error in statement: near "4.05519996684467": syntax error)
I imagine that, even if I get this to work, it will be horribly inefficient.
I thought there might have been some way to do this with read.csv.sql but this does not seem to work with open connection objects.