Fetch records from a previously executed query

Source: R/DBI.R

Fetch the next n elements (rows) from the result set and return them as a data.frame.

Methods in other packages

  • DatabaseConnector::dbFetch("DatabaseConnectorResult")

# S4 method for DatabaseConnectorResult
dbFetch(res, n = -1, ...)

Arguments

res

An object inheriting from DBIResult, created by dbSendQuery().

n

maximum number of records to retrieve per fetch. Use n = -1 or n = Inf to retrieve all pending records. Some implementations may recognize other special values.

...

Other arguments passed on to methods.

Value

dbFetch() always returns a data.frame

with as many rows as records were fetched and as many columns as fields in the result set, even if the result is a single value or has one or zero rows. An attempt to fetch from a closed result set raises an error. If the n argument is not an atomic whole number greater or equal to -1 or Inf, an error is raised, but a subsequent call to dbFetch() with proper n argument succeeds. Calling dbFetch() on a result set from a data manipulation query created by dbSendStatement()

can be fetched and return an empty data frame, with a warning.

Details

fetch() is provided for compatibility with older DBI clients - for all new code you are strongly encouraged to use dbFetch(). The default implementation for dbFetch() calls fetch() so that it is compatible with existing code. Modern backends should implement for dbFetch() only.

See also

Close the result set with dbClearResult() as soon as you finish retrieving the records you want.

Other DBIResult generics: DBIResult-class, dbBind(), dbClearResult(), dbColumnInfo(), dbGetInfo(), dbGetRowCount(), dbGetRowsAffected(), dbGetStatement(), dbHasCompleted(), dbIsReadOnly(), dbIsValid(), dbQuoteIdentifier(), dbQuoteLiteral(), dbQuoteString(), dbUnquoteIdentifier()