DBI (version 0.1-11)

fetch: 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 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.

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.

Details

See the notes for the various database server implementations.

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

# 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)