RODBC将数据框连接到sqlQuery中的表

Question

I've been using RODBC to connect to a DB2 database at work, and thus far everything works well. I can pull tables through sqlQuery, and join tables within the database before getting them back as a data frame. However, I often sped up the process in SAS by grabbing and manipulating tables, then joining them back to the database. When I try to do this in R, I'm having issues. I'd like it to go something like this.

library(RODBC)
channel <- odbcConnect(database stuff)
dataframe <- sqlQuery(channel, query)
.
.
manipulate data frame
. 
.
dataframe <- sqlQuery(channel, 
  "select * from dataframe as a INNER JOIN schema.table1 as b ON a.id=b.id")

The problem is that R doesn't recognize "dataframe". I think it has something to do with the "schema.dataframe" part, as I'm not sure what kind of "schema" the workspace would have. Is there a way to join a data frame to a table in a database in sqlQuery? Or can I somehow make the data frame a temporary table and join it from there?

Answer 1

You can either save dataframe as a table to your database with

sqlSave(channel, dataframe)

(see ?sqlSave for the options) and then do your query. Assuming that channel points to "schema":

dataframe <- sqlQuery(channel, 
  "select * from schema.dataframe as a INNER JOIN schema.table1 as b ON a.id=b.id")

Or you can use data.table() and do the join in R:

library(data.table)
dataframe <- data.table(dataframe)
setkey(dataframe, id)
table1 <- data.table(sqlQuery(channel, 
  "select * from schema.table1")
setkey(table1, id)
dataframe <- dataframe[table1, nomatch=0]

In both cases you would end up with a "auxiliary" object: schema.dataframe in the first case in your db, and table1 in R in the second case.