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

In easydb: Generic S3 Classes for Simple Database Interfaces

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

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 <[e-mail]>

See Also

edb, edbWrite,

edbNames, edbColnames.

Examples

# See related methods for detailed examples:


# (for example ?edbRead.RSQLite_SQLite) 


require( "easydb" ) 


methods( "edbRead" )

easydb documentation built on May 2, 2019, 4:47 p.m.