fetch
From DBI v0.1-11
by David James
Fetch records from a previously executed query
Fetch records from a previously executed query.
Usage
fetch(res, n, ...)
Arguments
- 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'sSELECT
orSELECT
-like statement, this objectres
is ty - 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.
Details
See the notes for the various database server implementations.
Value
- a data.frame with as many rows as records were fetched and as many columns as fields in the result set.
Note
Make sure you close the result set with dbClearResult
as soon as you finish retrieving the records you want.
Side Effects
As the R/Splus client fetches records the remote database server updates its cursor accordingly.
References
See the Database Interface definition document
DBI.pdf
in the base directory of this package
or
See Also
dbConnect
,
dbSendQuery
,
dbGetQuery
,
dbClearResult
,
dbCommit
,
dbGetInfo
,
dbReadTable
.
Examples
# 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)
Community examples
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