RxSqlServerData: Generate SqlServer Data Source Object

Article
07/15/2019

Description

This is the main generator for S4 class RxSqlServerData, which extends RxDataSource.

Usage

  RxSqlServerData(table = NULL, sqlQuery = NULL, connectionString = NULL, 
             rowBuffering = TRUE, returnDataFrame = TRUE, stringsAsFactors = FALSE, 
             colClasses = NULL, colInfo = NULL, rowsPerRead = 50000, verbose = 0,
             useFastRead = TRUE, server = NULL, databaseName = NULL, 
             user = NULL, password = NULL, writeFactorsAsIndexes = FALSE) 

 ## S3 method for class `RxSqlServerData':
head  (x, n = 6L, reportProgress = 0L,   ...  )
 ## S3 method for class `RxSqlServerData':
tail  (x, n = 6L, addrownums = TRUE, reportProgress = 0L,   ...  )

Arguments

`table`

NULL or character string specifying the table name. Cannot be used with sqlQuery.

`sqlQuery`

NULL or character string specifying a valid SQL select query. Cannot contain hidden characters such as tabs or newlines. Cannot be used with table. If you want to use TABLESAMPLE clause in sqlQuery, set rowBuffering argument to FALSE.

`connectionString`

NULL or character string specifying the connection string.

`rowBuffering`

logical specifying whether or not to buffer rows on read from the database. If you are having problems with your ODBC driver, try setting this to FALSE.

`returnDataFrame`

logical indicating whether or not to convert the result from a list to a data frame (for use in rxReadNext only). If FALSE, a list is returned.

`stringsAsFactors`

logical indicating whether or not to automatically convert strings to factors on import. This can be overridden by specifying "character" in colClasses and colInfo. If TRUE, the factor levels will be coded in the order encountered. Since this factor level ordering is row dependent, the preferred method for handling factor columns is to use colInfo with specified "levels".

`colClasses`

character vector specifying the column types to use when converting the data. The element names for the vector are used to identify which column should be converted to which type.

Allowable column types are:
- "logical" (stored as uchar),
- "integer" (stored as int32),
- "float32" (the default for floating point data for .xdf files),
- "numeric" (stored as float64 as in R),
- "character" (stored as string),
- "factor" (stored as uint32),
- "int16" (alternative to integer for smaller storage space),
- "uint16" (alternative to unsigned integer for smaller storage space),
- "Date" (stored as Date, i.e. float64)
Note for "factor" type, the levels will be coded in the order encountered. Since this factor level ordering is row dependent, the preferred method for handling factor columns is to use colInfo with specified "levels".
Note that equivalent types share the same bullet in the list above; for some types we allow both 'R-friendly' type names, as well as our own, more specific type names for .xdf data.
Note also that specifying the column as a "factor" type is currently equivalent to "string" - for the moment, if you wish to import a column as factor data you must use the colInfo argument, documented below.

`colInfo`

list of named variable information lists. Each variable information list contains one or more of the named elements given below. The information supplied for colInfo overrides that supplied for colClasses.

Currently available properties for a column information list are:
type - character string specifying the data type for the column. See colClasses argument description for the available types. Specify "factorIndex" as the type for 0-based factor indexes. levels must also be specified.
newName - character string specifying a new name for the variable.
description - character string specifying a description for the variable.
levels - character vector containing the levels when type = "factor". If the levels property is not provided, factor levels will be determined by the values in the source column. If levels are provided, any value that does not match a provided level will be converted to a missing value.
newLevels - new or replacement levels specified for a column of type "factor". It must be used in conjunction with the levels argument. After reading in the original data, the labels for each level will be replaced with the newLevels.
low - the minimum data value in the variable (used in computations using the F() function.
high - the maximum data value in the variable (used in computations using the F() function.

`rowsPerRead`

number of rows to read at a time.

`verbose`

integer value. If 0, no additional output is printed. If 1, information on the odbc data source type (odbc or odbcFast) is printed.

`...`

additional arguments to be passed directly to the underlying functions.

`x`

an RxSqlServerData object

`n`

positive integer. Number of rows of the data set to extract.

`addrownums`

logical. If TRUE, row numbers will be created to match the original data set.

`reportProgress`

integer value with options:

0: no progress is reported.
1: the number of processed rows is printed and updated.
2: rows processed and timings are reported.
3: rows processed and all timings are reported.

`useFastRead`

logical specifying whether or not to use a direct ODBC connection. On Linux systems, this is the only ODBC connection available. Note: useFastRead = FALSE is currently not supported in writing to SQL Server data source.

`server`

Target SQL Server instance. Can also be specified in the connection string with the Server keyword.

`databaseName`

Database on the target SQL Server instance. Can also be specified in the connection string with the Database keyword.

`user`

SQL login to connect to the SQL Server instance. SQL login can also be specified in the connection string with the uid keyword.

`password`

Password associated with the SQL login. Can also be specified in the connection string with the pwd keyword.

`writeFactorsAsIndexes`

logical. If TRUE, when writing to an RxOdbcData data source, underlying factor indexes will be written instead of the string representations.

Details

The tail method is not functional for this data source type and will report an error.

The user and password arguments take precedence over equivalent information provided within the connectionString argument. If, for example, you provide the user name in both the connectionString and user arguments, the one in connectionString is ignored.

Value

object of class RxSqlServerData.

Author(s)

Microsoft Corporation Microsoft Technical Support

Examples


 ## Not run:

# Create an RxSqlServerData data source

# Note: for improved security, read connection string from a file, such as
# sqlServerConnString <- readLines("sqlServerConnString.txt")

sqlServerConnString <- "SERVER=hostname;DATABASE=RevoTestDB;UID=DBUser;PWD=Password;"

sqlServerDataDS <- RxSqlServerData(sqlQuery = "SELECT * FROM claims",
                              connectionString = sqlServerConnString)

# Create an xdf file name
claimsXdfFileName <- file.path(tempdir(), "importedClaims.xdf")

# Import the data into the xdf file
rxImport(sqlServerDataDS, claimsXdfFileName, overwrite = TRUE)

# Read xdf file into a data frame
claimsIn <- rxDataStep(claimsXdfFileName)
head(claimsIn)
## End(Not run)

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