Mapping to SAS Constructs

In OLE DB, a rowset is a type of cursor over a table that consists of rows and columns. The intersection of each row and column identifies a cell of data. Every cell in a specific column is of the same data type. The OLE DB concept of a table corresponds directly to the SAS data set.

A data set consists of variables and observations. A variable defines a cell of data in an observation. Variables are like columns, and observations are like rows. In fact, these OLE DB terms and SAS terms can be used interchangeably.

The following table compares the members of the DBCOLUMNINFO structure with the COLUMNS schema rowset columns and describes how they all correspond to SAS constructs:

DBCOLUMNINFO Structure Members Compared with COLUMNS Schema Rowset Columns and the Corresponding SAS Constructs

DBCOLUMNINFO Member	COLUMNS Schema Rowset Column	SAS Data Model	Comments
pwszName columnid	COLUMN_NAME	variable name
pTypeInfo	not available	not applicable	Reserved by Microsoft for future use
iOrdinal	ORDINAL_POSITION	variable number
dwFlags	not applicable	not applicable
ulColumnSize	CHARACTER_MAXIMUM_LENGTH and CHARACTER_OCTET_LENGTH	variable length	Defines the maximum length of this column/variable
wType	DATA_TYPE	variable type	When accessing Unicode data sets, character variables are mapped to DBTYPE__WSTR. When accessing data sets that are not Unicode, character variables are mapped to DBTYPE_STR. Numeric variables are mapped to DBTYPE_R8 for data sets in all encodings.
bPrecision	NUMERIC_PRECISION	not applicable
bScale	not applicable	not applicable
not available	DESCRIPTION	variable label
not available	IS_NULLABLE	not available	Indicates that a cell in this column could be set to "missing"

Members of the DBCOLUMINFO structure and columns in the COLUMNS schema rowset that are not represented in this table either do not map to SAS constructs and are not supported, or they do not map directly to SAS column metadata.