fetch-methods {RPostgreSQL} | R Documentation |
Fetch records from a previously executed query
Description
This method is a straight-forward implementation of the corresponding generic function.
Details
The RPostgreSQL
implementations retrieves only n
records,
and if n
is missing it only returns up to fetch.default.rec
as specified in the call to PostgreSQL
(500 by default).
Methods
- res
-
an
PostgreSQLResult
object. - n
-
maximum number of records to retrieve per fetch. Use
n = -1
to retrieve all pending records; use a value ofn = 0
for fetching the default number of rowsfetch.default.rec
defined in thePostgreSQL
initialization invocation. - ...
currently not used.
References
See the Database Interface definition document
DBI.pdf
in the base directory of this package
or https://cran.r-project.org/package=DBI.
See Also
PostgreSQL
,
dbConnect
,
dbSendQuery
,
dbGetQuery
,
dbClearResult
,
dbCommit
,
dbGetInfo
,
dbReadTable
.
Examples
## Not run:
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, user = "ruser",password = "123456",dbname = "status")
res <- dbSendQuery(con, statement = paste(
"SELECT w.category, w.cost, p.type",
"FROM items w, sales P",
"WHERE w.category = p.type",
"ORDER BY w.cost"))
# 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)