| dbManager {RSQLite} | R Documentation |
This function creates a driver manager object that allows you to connect to a Database Systems (DBMS) specified in its argument.
dbManager(obj, ...)
mgr |
a character string specifying the DBMS, e.g., "SQLite", "MySQL", "Oracle", "Informix". |
... |
additional parameters may be specified for the actual database engine.
E.g., the SQLite implementation allows you to specify the maximum
number of open connection and a default maximum number of records
to be transferred from the database.
See the individual manager functions for details,
e.g., MySQL, SQLite,
Oracle.
|
This object is a singleton, that is, if you invoke this function again, it will return the same initialized object.
An object that extends dbManager and
dbObjectId in a database-specific manner.
For instance dbManager("SQLite") produces
an object of class SQLiteManager and
is equivalent to using SQLite.
Similarly dbManager("Oracle") produces
an OracleManager object and its equivalent
to invoking Oracle.
This object is required to create connections
to one or several database engines.
The R/S client part of the database communication is initialized,
connecting to the database engine needs to be done through
calls to dbConnect.
See the Omega Project for Statistical Computing at http://www.omegahat.org for more details on the R/S database interface.
On database managers:
On connections, SQL statements and resultSets:
dbExecStatement
dbExec
fetch
quickSQL
On transaction management:
On meta-data:
describe
getVersion
getDatabases
getTables
getFields
getCurrentDatabase
getTableIndices
getException
getStatement
hasCompleted
getRowCount
getAffectedRows
getNullOk
getInfo
# create a SQLite instance and create one connection.
> m <- dbManager("SQLite")
> m
SQLiteManager 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, verbose = F)
SQLiteManager id = (7269)
Max connections: 16
Conn. processed: 1
Default records per fetch: 500
Open connections: 1
# 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
SQLiteResultSet 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
# Extract meta-data information. What SQLite databases are there
# available on host "wyner"
> getDatabases(m, host = "wyner")
Database
1 mysql
2 opto
3 test
4 iptraffic
5 fraud
> # What tables are there in the "opto" database?
> dbTables(m, dbname = "opto", host = "wyner")
Tables in opto
1 PBCT
2 PURGE
3 WL
4 liv25
5 liv85