dbReadTable {DBI}R Documentation

Convenience functions for Importing/Exporting DBMS tables

Description

These functions mimic their R/Splus counterpart get, assign, exists, remove, and objects, except that they generate code that gets remotely executed in a database engine.

Usage

  dbReadTable(conn, name, ...)
  dbWriteTable(conn, name, value, ...)
  dbExistsTable(conn, name, ...)
  dbRemoveTable(conn, name, ...)

Usage

  dbReadTable(conn, name, row.names = "row_names", ...)
  dbWriteTable(conn, name, value, row.names = T, ...,
              overwrite = F, append = F)
  dbExistsTable(conn, name, ...)
  dbRemoveTable(conn, name, ...)

Arguments

conn

a database connection object.

name

a character string specifying a DBMS table name.

value

a data.frame (or coercible to data.frame).

row.names

in the case of dbReadTable, this argument can be a string or an index specifying the column in the DBMS table to be used as row.names in the output data.frame (a NULL, "", or 0 specifies that no column should be used as row.names in the output).

In the case of dbWriteTable, this argument should be a logical specifying whether the row.names should be output to the output DBMS table; if TRUE, the extra field name will be whatever the S identifier "row.names" maps to the DBMS (see make.db.names).

overwrite

a logical specifying whether to overwrite an existing table or not. Its default is FALSE.

append

a logical specifying whether to append to an existing table in the DBMS. Its default is FALSE.

...

any optional arguments that the underlying database driver supports.

Value

dbReadTable returns a data.frame; all other functions return TRUE or FALSE denoting whether the operation was successful or not.

Side Effects

A DBMS statement is generated and remotely executed on a database engine; the result set it produces is fetched in its entirety. These operations may failed if the underlying database driver runs out of available connections and/or result sets, or the operation violates DBMS integrity constraints (e.g., attempting to write duplicate values on a field that's defined as a primary key).

The semantics of assign are slightly extended to allow overwriting or appending to an existing table.

Note

The translation of identifiers between R/Splus and SQL is done through calls to make.names and make.db.names, but we cannot guarantee that the conversion is reversible. For details see make.db.names.

References

See the Database Interface definition document DBI.pdf in the base directory of this package or http://developer.r-project.org/db.

See Also

dbDriver, dbConnect, dbSendQuery, dbGetQuery, fetch, dbCommit, dbGetInfo, dbListTables, dbReadTable.

Examples

## Not run: 
conn <- dbConnect("MySQL", group = "vitalAnalysis")
con2 <- dbConnect("ODBC", "dsn", "user", "pwd")
if(dbExistsTable(con2, "fuel_frame")){
   fuel.frame <- dbReadTable(con2, "fuel_frame")
   dbRemoveTable(conn, "fuel_frame")
   dbWriteTable(conn, "fuel_frame", fuel.frame)
}
if(dbExistsTable(conn, "RESULTS")){
   dbWriteTable(conn, "RESULTS", results2000, append = T)
else
   dbWriteTable(conn, "RESULTS", results2000)
}

## End(Not run)
[Package DBI version 0.2-5 Index]