dbFetch
From DBI v0.5-1
by Kirill Müller
Fetch records from a previously executed query
Fetch the next n elements (rows) from the result set and return them
as a data.frame.
Usage
dbFetch(res, n = -1, ...)
fetch(res, n = -1, ...)Arguments
- res
- An object inheriting from
DBIResult. - n
- maximum number of records to retrieve per fetch. Use
n = -1to retrieve all pending records. Some implementations may recognize other special values. - ...
- Other arguments passed on to methods.
Details
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 are free to provide methods for dbFetch
only.
Value
-
a data.frame with as many rows as records were fetched and as many
columns as fields in the result set.
See Also
close the result set with dbClearResult as soon as you
finish retrieving the records you want.
Other DBIResult generics: DBIResult-class,
SQL, dbBind,
dbClearResult, dbColumnInfo,
dbGetInfo, dbGetRowCount,
dbGetRowsAffected,
dbGetStatement,
dbHasCompleted, dbIsValid
Examples
library(DBI)
con <- dbConnect(RSQLite::SQLite(), ":memory:")
dbWriteTable(con, "mtcars", mtcars)
# Fetch all results
rs <- dbSendQuery(con, "SELECT * FROM mtcars WHERE cyl = 4")
dbFetch(rs)
dbClearResult(rs)
# Fetch in chunks
rs <- dbSendQuery(con, "SELECT * FROM mtcars")
while (!dbHasCompleted(rs)) {
chunk <- dbFetch(rs, 10)
print(nrow(chunk))
}
dbClearResult(rs)
dbDisconnect(con)
Community examples
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