RSQLite (version 0.2-1)

dbConnect: Create a connection to a DBMS

Description

Connect to a DBMS going through the appropriate authorization procedure

Usage

dbConnect(mgr, ...)

Arguments

mgr

a dbManager object, a character string specifying the DBMS, e.g., "MySQL", "Oracle", "Informix", or another dbConnect object.

...

authorization arguments needed by the DBMS instance; these typically include user, password, dbname, host, port, etc. For details see the appropriate dbManager.

Value

• An object that extends dbConnect and dbObjectId in a database-specific manner. For instance dbConnect("MySQL") produces an object of class MySQLConnection.

  This object is used to direct SQL commands to the database engine.

Side Effects

A connection between R/S and the database server is established, and the R/S program becomes a client of the database engine. Typically the connections is through the TCP/IP protocol, but this will depend on vendor-specific details.

notes

Make sure you close the connection using close(con) when it is not longer needed.

References

See the Omega Project for Statistical Computing at http://www.omegahat.org for more details on the R/S database interface.

Details

Some implementations (e.g., RMySQL, ROracle, RSQLite) may allow you to have multiple connecions open, so you may invoke this function repeatedly assigning its output to different objects.

See Also

On database managers:

dbManager SQLite load unload

On connections, SQL statements and resultSets:

dbExecStatement dbExec fetch quickSQL

On transaction management:

commit rollback

On meta-data:

describe getVersion getDatabases getTables getFields getCurrentDatabase getTableIndices getException getStatement hasCompleted getRowCount getAffectedRows getNullOk getInfo

Examples

# create a MySQL instance and create one connection.
> m <- dbManager("MySQL")
> m
MySQLManager id = (7269) 

# open the connection using user, passsword, etc., as
# specified in the file \file{\$HOME/.my.cnf}
> con <- dbConnect(m)    

# Let's look at the status of the manager
> describe(m)
MySQLManager id = (7269) 
  Max  connections: 16 
  Conn. processed: 1 
  Default records per fetch: 500 

# Run an SQL statement by creating first a resultSet object
> rs <- dbExecStatement(con, 
         statement = "SELECT w.laser_id, w.wavelength, p.cut_off 
                      FROM WL w, PURGE P
                      WHERE w.laser_id = p.laser_id
                      SORT BY w.laser_id")
> rs
MySQLResultSet id = (12629,1,3)

# we now fetch records from the restulSet into a data.frame
> data <- fetch(rs, n = -1)   # extract all rows
> dim(data)
[1] 1779  18