fetch {DBI} | R Documentation |
Fetch records from a previously executed query.
fetch(res, n, ...)
res |
a result set object (one whose class extends DBIResult ).
This object needs to be the result of a statement that produces
output, such as SQL's SELECT or SELECT -like statement,
this object res is typically produced by a call to
or dbSendQuery .
|
n |
maximum number of records to retrieve per fetch.
Use n = -1 to retrieve all pending records.
Some implementations may recognize other special values.
|
... |
any other database-engine specific arguments. |
See the notes for the various database server implementations.
a data.frame with as many rows as records were fetched and as many columns as fields in the result set.
As the R/Splus client fetches records the remote database server updates its cursor accordingly.
Make sure you close the result set with dbClearResult
as soon as you finish retrieving the records you want.
See the Database Interface definition document
DBI.pdf
in the base directory of this package
or http://developer.r-project.org/db.
dbConnect
,
dbSendQuery
,
dbGetQuery
,
dbClearResult
,
dbCommit
,
dbGetInfo
,
dbReadTable
.
## Not run: # Run an SQL statement by creating first a resultSet object drv <- dbDriver("ODBC") con <- dbConnect(drv, ...) res <- dbSendQuery(con, statement = paste( "SELECT w.laser_id, w.wavelength, p.cut_off", "FROM WL w, PURGE P", "WHERE w.laser_id = p.laser_id", "ORDER BY w.laser_id")) # we now fetch the first 100 records from the resultSet into a data.frame data1 <- fetch(res, n = 100) dim(data1) dbHasCompleted(res) # let's get all remaining records data2 <- fetch(res, n = -1) ## End(Not run)