edbRead: Read all or part of a table in a database (referenced by...

Description Usage Arguments Author(s) See Also Examples

View source: R/easydb.R

Description

Read all or part of a table in a database (referenced by 'edb').

Generic function that call class-specific method corresponding

to the class of the edb object provided.

Usage

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edbRead(edb, tableName, sRow = NULL, sCol = NULL, sRowOp = c("AND", 


    "OR")[1], formatCol = NULL, distinct = FALSE, orderBy = NULL, 


    ...)

Arguments

edb

An object of class 'edb', such as returned by edb.

tableName

Single character string. Name of the table to read in 'edb'.

sRow

A list of named items. List of contrains/criterion to be applied

on tableName to retrieve a subset of rows. Each item in

sRow must be named after the columns on which the constrain

apply. The (vector of) value(s) of each items are the possible values

that can be retrieved. Values can be character or numeric. If NULL

(the default), all values are returned.

sCol

A vector of character strings. Names of the columns to retrieve.

sRowOp

A single character string. Operator to be used to combine multiple

constrains in sRow. Possible values are "OR" or "AND". Default value

is "AND".

formatCol

If not NULL, a named list of functions to be applied to certain columns

after the data has been extracted from the database. The name of each list

item gives the column to process, and the value of each item gives the

function that must be applied. For instance

formatCol = list("DATE"=as.Date) will apply the function

as.Date to the column "DATE".

distinct

Single logical. If TRUE, unique values in the result table will

be returned, using the SELECT DISTINCT SQL statement.

This is equivalent to applying unique to the

data.frame returned by the function, except that the action is

performed inside the database (not in R).

orderBy

Vector of character strings, or NULL (the default). If non NULL,

vector of column names that must be used to sort the result table.

Column names may be followed by a space and 'DESC' if the column

must be sorted in a descending order ('ASC', ascending, is the

default). For example, oderBy = "MYCOLUMN DESC". This

operation is performed in the database with SQL ORDER BY

statement and is equivalent to ordering the data in R with

order.

...

Additional parameters to be passed to class-specific method. See

methods("edbRead")

Author(s)

Julien MOEYS <[email protected]>

See Also

edb, edbWrite,

edbNames, edbColnames.

Examples

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# See related methods for detailed examples:


# (for example ?edbRead.RSQLite_SQLite) 


require( "easydb" ) 


methods( "edbRead" )

easydb documentation built on May 31, 2017, 2:06 a.m.