dbFetch {DBI} | R Documentation |
Fetch the next n
elements (rows) from the result set and return them
as a data.frame.
dbFetch(res, n = -1, ...) fetch(res, n = -1, ...)
res |
An object inheriting from |
n |
maximum number of records to retrieve per fetch. Use |
... |
Other arguments passed on to methods. |
fetch
is provided for compatibility with older DBI clients - for all
new code you are strongly encouraged to use dbFetch
. The default
method for dbFetch
calls fetch
so that it is compatible with
existing code. Implementors should provide methods for both fetch
and
dbFetch
until fetch
is deprecated in 2015.
a data.frame with as many rows as records were fetched and as many columns as fields in the result set.
close the result set with dbClearResult
as soon as you
finish retrieving the records you want.
Other DBIResult generics: dbClearResult
,
dbColumnInfo
, dbGetRowCount
,
dbGetRowsAffected
,
dbGetStatement
,
dbHasCompleted
if (!require("RSQLite")) { con <- dbConnect(RSQLite::SQLite(), ":memory:") dbWriteTable(con, "mtcars", mtcars) # Fetch all results res <- dbSendQuery(con, "SELECT * FROM mtcars WHERE cyl = 4") dbFetch(res) dbClearResult(res) # Fetch in chunks res <- dbSendQuery(con, "SELECT * FROM mtcars") while (!dbHasCompleted(res)) { chunk <- fetch(res, 10) print(nrow(chunk)) } dbClearResult(res) dbDisconnect(con) }