fetch {DBI}R Documentation

Fetch records from a previously executed query

Description

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'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.

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.

Side Effects

As the R/Splus client fetches records the remote database server updates its cursor accordingly.

Note

Make sure you close the result set with dbClearResult as soon as you finish retrieving the records you want.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or http://developer.r-project.org/db.

See Also

dbConnect, dbSendQuery, dbGetQuery, dbClearResult, dbCommit, dbGetInfo, dbReadTable.

Examples

## 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)

[Package DBI version 0.2-4 Index]