| dbReadTable-methods {DBI} | R Documentation |
These functions mimic their R/S-Plus 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, an extra field whose name will be
whatever the R/S-Plus 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).
dbWritetable slightly extend the semantics of assign to
allow overwriting or appending to an existing table.
The translation of identifiers between R/S-Plus 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("Oracle", username = "user", password = "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)