1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
|
% $Id: dbReadTable-methods.Rd,v 0.1 2008/07/23 02:38:31 psk Exp $
\name{dbReadTable-methods}
\docType{methods}
\alias{dbReadTable-methods}
\alias{dbWriteTable-methods}
\alias{dbExistsTable-methods}
\alias{dbRemoveTable-methods}
\alias{dbReadTable,PostgreSQLConnection,character-method}
\alias{dbWriteTable,PostgreSQLConnection,character,character-method}
\alias{dbWriteTable,PostgreSQLConnection,character,data.frame-method}
\alias{dbExistsTable,PostgreSQLConnection,character-method}
\alias{dbRemoveTable,PostgreSQLConnection,character-method}
\title{
Convenience functions for Importing/Exporting DBMS tables
}
\description{
These functions mimic their R/S-Plus counterpart
\code{get},
\code{assign},
\code{exists},
\code{remove}, and
\code{objects},
except that they generate code that gets remotely executed
in a database engine.
}
\section{Methods}{\describe{
\item{conn}{
an \code{PostgreSQLConnection} database connection object.
}
\item{name}{
a character string specifying a table name.
}
\item{value}{
a data.frame (or coercible to data.frame).
When the \code{value} is a character string, it is assumed to be a file name containing the data to be loaded;
The implementation is INCOMPLETE and should not be used in current state.
}
\item{row.names}{
UNTESTED;
in the case of \code{dbReadTable}, this argument can be a string or
an index specifying the column in the DBMS table to be used as
\code{row.names} in the output data.frame (a \code{NULL}, \code{""}, or 0
specifies that no column should be used as \code{row.names} in the output).
In the case of \code{dbWriteTable}, this argument should be a logical
specifying whether the \code{row.names} should be output to the
output DBMS table; if \code{TRUE}, an extra field whose name will be
whatever the R/S-Plus identifier \code{"row.names"} maps to the DBMS
(see \code{\link[DBI]{make.db.names}}).
}
\item{overwrite}{
a logical specifying whether to overwrite an existing table
or not. Its default is \code{FALSE}.
}
\item{append}{
a logical specifying whether to append to an existing table
in the DBMS. Its default is \code{FALSE}.
}
\item{allow.keywords}{
\code{dbWriteTable} accepts a logical \code{allow.keywords}
to allow or prevent PostgreSQL reserved identifiers to be used as
column names. By default it is \code{FALSE}.
}
\item{dots}{
optional arguments.
When \code{dbWriteTable} is used to import data from a file,
you may optionally specify \code{header=}, \code{row.names=},
\code{col.names=}, \code{sep=}, \code{eol=}, \code{field.types=},
\code{skip=}, and \code{quote=}. NOT FULLY IMPLEMENTED YET.
\code{header} is a logical indicating whether the first data line
(but see \code{skip}) has a header or not. If missing, it value
is determined following \code{\link{read.table}} convention,
namely, it is set to TRUE if and only if the first row has one
fewer field that the number of columns.
\code{row.names} is a logical to specify whether the first column
is a set of row names. If missing its default follows the
\code{\link{read.table}} convention.
\code{col.names} a character vector with column names; column names are quoted to work as SQL identifiers.
Thus, the column names are case sensitive and \code{\link[DBI]{make.db.names}} will NOT be used here.
\code{sep=} specifies the field separator, and its default is \code{','}.
\code{eol=} specifies the end-of-line delimiter, and its default is
\code{'\n'}.
\code{skip} specifies number of lines to skip before reading the data,
and it defaults to 0.
\code{field.types} is a list of named field SQL types where
\code{names(field.types)} provide the new table's column names
(if missing, field types are inferred using \code{\link[DBI]{dbDataType}}).
}
}
}
\value{
A \code{data.frame} in the case of \code{dbReadTable}; otherwise a logical
indicating whether the operation was successful.
}
\note{
dbWriteTable creates additional column in the database, while dbReadTable
reads that column by default. So, it is not symmetrical in its current implementation.
the backend raw_names may change in future versions.
}
\references{
See the Database Interface definition document
\code{DBI.pdf} in the base directory of this package
or \url{https://cran.r-project.org/package=DBI}.
}
\seealso{
\code{\link{PostgreSQL}},
\code{\link[DBI]{isSQLKeyword}},
\code{\link[DBI]{dbDriver}},
\code{\link[DBI]{dbConnect}},
\code{\link[DBI]{dbSendQuery}},
\code{\link[DBI]{dbGetQuery}},
\code{\link[DBI]{fetch}},
\code{\link[DBI]{dbCommit}},
\code{\link[DBI]{dbGetInfo}},
\code{\link[DBI]{dbListTables}},
\code{\link[DBI]{dbReadTable}}.
}
\examples{\dontrun{
conn <- dbConnect("PostgreSQL", dbname = "wireless")
if(dbExistsTable(conn, "frame_fuel")){
dbRemoveTable(conn, "frame_fuel")
dbWriteTable(conn, "frame_fuel", fuel.frame)
}
if(dbExistsTable(conn, "RESULTS")){
dbWriteTable(conn, "RESULTS", results2000, append = T)
else
dbWriteTable(conn, "RESULTS", results2000)
}
}
}
\keyword{methods}
\keyword{interface}
\keyword{database}
% vim: syntax=tex
|
