[R-sig-DB] R and PostgreSQL - Writing data?

[Dirk Eddelbuettel]

On 30 November 2012 at 15:05, James David Smith wrote:
| Hi all,
| 
| Sorry for the thread re-activation. I was wondering if anyone has
| successfully used the syntax below with the library RPostgreSQL?

Nope. 

I always expand the strings explicitly. It would be news to me of that
worked.  Good news, for sure, but still news...

Dirk
 

| dbGetQuery(con, "update foo set sal = :1 where empno = :2",
|            data = dat[,c("SAL","EMPNO")])
| 
| I've been messing about with it but can't get it to work. I get the error:
| 
| Error in postgresqlQuickSQL(conn, statement, ...) :
|   unused argument(s) (data = list(bc = c(NA, NA, NA etc.
| 
| Thanks
| 
| James
| 
| 
| 
| On 28 September 2012 17:13, Denis Mukhin <denis.x.mukhin using oracle.com> wrote:
| > James,
| >
| > I have never tried RPostgreSQL before but in ROracle which is also a DBI based interface you can do something like this:
| >
| > library(ROracle)
| > con <- dbConnect(Oracle(), "scott", "tiger")
| > dbGetQuery(con, "create table foo as select * from emp")
| >
| > dat <- dbGetQuery(con, "select * from foo")
| > dat$SAL <- dat$SAL*10
| > dbGetQuery(con, "update foo set sal = :1 where empno = :2",
| >            data = dat[,c("SAL","EMPNO")])
| > dbCommit(con)
| > dbGetQuery(con, "select * from foo")
| >
| > dbGetQuery(con, "drop table foo purge")
| > dbDisconnect(con)
| >
| > Denis
| >
| > -----Original Message-----
| > From: Sean Davis [mailto:sdavis2 using mail.nih.gov]
| > Sent: Friday, September 28, 2012 11:43 AM
| > To: James David Smith
| > Cc: r-sig-db using r-project.org
| > Subject: Re: [R-sig-DB] R and PostgreSQL - Writing data?
| >
| > On Fri, Sep 28, 2012 at 10:36 AM, James David Smith <james.david.smith using gmail.com> wrote:
| >> Hi Sean,
| >>
| >> Thanks for the reply. I'm familiar with UPDATE queries when working in
| >> PostgreSQL, but not from within R. Would it look something like this?
| >>
| >> dbWriteTable(con, " UPDATE table SET ucam_no2 =
| >> 'ucam_no2$interpolated_data' ")
| >>
| >> My problem is how to get the R data 'within' my SQL statement I think.
| >
| > To do an update, you'll need to loop through your data.frame and issue a dbSendQuery().  To create the SQL string, I often use something
| > like:
| >
| > sprintf("UPDATE originalTable SET ucam_no2=%f WHERE originalTable.id = %d",....)
| >
| > You can't do this in one step, unfortunately.  This is how UPDATE works and has nothing to do with R.
| >
| > Sean
| >
| >
| >>
| >> On 28 September 2012 15:19, Sean Davis <sdavis2 using mail.nih.gov> wrote:
| >>> On Fri, Sep 28, 2012 at 10:14 AM, James David Smith
| >>> <james.david.smith using gmail.com> wrote:
| >>>> Dear all,
| >>>>
| >>>> Sorry if this isn't quite the right place, but it's the first time
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| >>
| >>>> I've posted here. My issue is to do with writing to a PostgreSQL
| >>>> database from within R. My situation is best explained by some R
| >>>> code to start:
| >>>>
| >>>> #Connect to the database
| >>>> con <- dbConnect(PostgreSQL(), user="postgres", password="password",
| >>>> dbname="database")
| >>>>
| >>>> #Get some data out of the database.
| >>>> ucam_no2$original_data <- dbGetQuery(con, "select ucam_no2 FROM
| >>>> table")
| >>>>
| >>>> This returns say 10000 rows of data, but there is only data in about
| >>>> half of those rows. What I want to do is interpolate the missing
| >>>> data so I do this:
| >>>>
| >>>> #Generate some data
| >>>> ucam_no2$interpolated_data <- na.approx(ucam_data$ucam_no2, na.rm =
| >>>> FALSE)
| >>>>
| >>>> This works well and I now have 10000 rows of data with no empty cells.
| >>>> I now want to write this back into my PostgresSQL database. Into the
| >>>> same row that I took the data from in the first place. But I don't
| >>>> know how. I can write to a new table with something like the below,
| >>>> but what I'd really like to do is put the data back into the table I
| >>>> got it from.
| >>>>
| >>>> # Try to write the data back
| >>>> dbWriteTable(con, "new_data", ucam_no2$interpolated_data)
| >>>
| >>> Hi, James.
| >>>
| >>> You'll need to look into doing a SQL UPDATE.  That is the standard
| >>> way to "put data back into the table I got it from".
| >>>
| >>> Sean
| >
| > _______________________________________________
| > R-sig-DB mailing list -- R Special Interest Group R-sig-DB using r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-db
| >
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-- 
Dirk Eddelbuettel | edd using debian.org | http://dirk.eddelbuettel.com