fetch-methods {RSQLite} | R Documentation

## Fetch records from a previously executed query

### Description

This method is a straight-forward implementation of the corresponding generic function.

### Details

The `RSQLite` implementations retrieves all records into a buffer internally managed by the RSQLite driver (thus this memory in not managed by R but its part of the R process), and `fetch` simple returns records from this internal buffer.

### Methods

res
  an `SQLiteResult` object.
n
  maximum number of records to retrieve per fetch. Use `n = -1` to retrieve all pending records; use a value of `n = 0` for fetching the default number of rows `fetch.default.rec` defined in the `SQLite` initialization invocation.
...
  currently not used.

### References

See the Database Interface definition document `DBI.pdf` in the base directory of this package or http://stat.bell-labs.com/RS-DBI.

### See Also

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

### Examples

    ## Don't run:
    drv <- dbDriver("SQLite")
    con <- dbConnect(drv, dbname = "sqlite.db")
    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 Don't run

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