dbReadTable {DBI} | R Documentation |
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.
dbReadTable(conn, name, row.names = "row_names", ...) dbWriteTable(conn, name, value, row.names = T, ..., overwrite = F, append = F) dbExistsTable(conn, name, ...) dbRemoveTable(conn, name, ...)
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. |
dbReadTable
returns a data.frame; all other functions
return TRUE
or FALSE
denoting whether the operation
was successful or not.
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.
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
.
See the Database Interface definition document
DBI.pdf
in the base directory of this package
or http://developer.r-project.org/db.
dbDriver
,
dbConnect
,
dbSendQuery
,
dbGetQuery
,
fetch
,
dbCommit
,
dbGetInfo
,
dbListTables
,
dbReadTable
.
## 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)