Data Type Mapping in ITableDefinition
When creating tables by using the ITableDefinition::CreateTable function, the SQL 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 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 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 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 Native Client OLE DB provider inspects the DBCOLUMNDESC rgPropertySets member. If DBPROP_COL_FIXEDLENGTH is VARIANT_TRUE, the SQL Native Client OLE DB provider maps the type to binary. If the value of the property is VARIANT_FALSE, the SQL 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 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 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 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 Native Client OLE DB provider inspects the DBCOLUMNDESC rgPropertySets member. If DBPROP_COL_FIXEDLENGTH is VARIANT_TRUE, the SQL Native Client OLE DB provider maps the type to char. If the value of the property is VARIANT_FALSE, the SQL 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 |
|
DBTYPE_UI1 |
tinyint |
|
DBTYPE_WSTR |
nchar, nvarchar, ntext, or nvarchar(max) |
The SQL Native Client OLE DB provider inspects the ulColumnSize member of the DBCOLUMNDESC structure. Based on the value, the SQL 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 Native Client OLE DB provider inspects the DBCOLUMNDESC rgPropertySets member. If DBPROP_COL_FIXEDLENGTH is VARIANT_TRUE, the SQL Native Client OLE DB provider maps the type to nchar. If the value of the property is VARIANT_FALSE, the SQL 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 |
[!NOTA] When creating a new table, the SQL 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.