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Data Type Mapping in ITableDefinition

When creating tables by using the ITableDefinition::CreateTable function, the SQL Server Native Client OLE DB provider consumer can specify SQL Server data types in the pwszTypeName member of the DBCOLUMNDESC array that is passed. If the consumer specifies the data type of a column by name, OLE DB data type mapping, represented by the wType member of the DBCOLUMNDESC structure, is ignored.

When specifying new column data types with OLE DB data types using the DBCOLUMNDESC structure wType member, the SQL Server Native Client OLE DB provider maps OLE DB data types as follows.

OLE DB data type

SQL Server

data type

Additional information

DBTYPE_BOOL

bit

DBTYPE_BYTES

binary, varbinary, image, or varbinary(max)

The SQL Server Native Client OLE DB provider inspects the ulColumnSize member of the DBCOLUMNDESC structure. Based on the value, and version of the SQL Server instance, the SQL Server Native Client OLE DB provider maps the type to image.

If the value of ulColumnSize is smaller than the maximum length of a binary data type column, then the SQL Server Native Client OLE DB provider inspects the DBCOLUMNDESC rgPropertySets member. If DBPROP_COL_FIXEDLENGTH is VARIANT_TRUE, the SQL Server Native Client OLE DB provider maps the type to binary. If the value of the property is VARIANT_FALSE, the SQL Server Native Client OLE DB provider maps the type to varbinary. In either case, the DBCOLUMNDESC ulColumnSize member determines the width of the SQL Server column created.

DBTYPE_CY

money

DBTYPE_DBTIMESTAMP

datetime

DBTYPE_GUID

uniqueidentifier

DBTYPE_I2

smallint

DBTYPE_I4

int

DBTYPE_NUMERIC

numeric

The SQL Server Native Client OLE DB provider inspects the DBCOLUMDESC bPrecision and bScale members to determine precision and scale for the numeric column.

DBTYPE_R4

real

DBTYPE_R8

float

DBTYPE_STR

char, varchar, text, or varchar(max)

The SQL Server Native Client OLE DB provider inspects the ulColumnSize member of the DBCOLUMNDESC structure. Based on the value and version of the SQL Server instance, the SQL Server Native Client OLE DB provider maps the type to text.

If the value of ulColumnSize is smaller than the maximum length of a multibyte character data type column, then the SQL Server Native Client OLE DB provider inspects the DBCOLUMNDESC rgPropertySets member. If DBPROP_COL_FIXEDLENGTH is VARIANT_TRUE, the SQL Server Native Client OLE DB provider maps the type to char. If the value of the property is VARIANT_FALSE, the SQL Server Native Client OLE DB provider maps the type to varchar. In either case, the DBCOLUMNDESC ulColumnSize member determines the width of the SQL Server column created.

DBTYPE_UDT

UDT

The following information is used in DBCOLUMNDESC structures by ITableDefinition::CreateTable when UDT columns are required:

  • pwSzTypeName is ignored.

  • rgPropertySets must include a DBPROPSET_SQLSERVERCOLUMN property set as described in the section on DBPROPSET_SQLSERVERCOLUMN, in Using User-Defined Types.

DBTYPE_UI1

tinyint

DBTYPE_WSTR

nchar, nvarchar, ntext, or nvarchar(max)

The SQL Server Native Client OLE DB provider inspects the ulColumnSize member of the DBCOLUMNDESC structure. Based on the value, the SQL Server Native Client OLE DB provider maps the type to ntext.

If the value of ulColumnSize is smaller than the maximum length of a Unicode character data type column, then the SQL Server Native Client OLE DB provider inspects the DBCOLUMNDESC rgPropertySets member. If DBPROP_COL_FIXEDLENGTH is VARIANT_TRUE, the SQL Server Native Client OLE DB provider maps the type to nchar. If the value of the property is VARIANT_FALSE, the SQL Server Native Client OLE DB provider maps the type to nvarchar. In either case, the DBCOLUMNDESC ulColumnSize member determines the width of the SQL Server column created.

DBTYPE_XML

XML

NoteNote

When creating a new table, the SQL Server Native Client OLE DB provider maps only the OLE DB data type enumeration values specified in the preceding table. Attempting to create a table with a column of any other OLE DB data type generates an error.

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