.Net中Access数据格式对应

INFO: OleDbType Enumeration vs. Microsoft Access Data Types

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Article ID : 320435 Last Review : February 22, 2007 Revision : 4.1

This article was previously published under Q320435

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SUMMARY

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List of the Most Common Data Type Mappings

REFERENCES

SUMMARY

This article describes how the Microsoft .NET Platform OLE DB types map to the Microsoft Access data types for columns.

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MORE INFORMATION

When you use the Access interface to design a table, you see several choices for field types that do not match to database data types. This is because these "types" are just display formats and do not determine the data type. Access uses other properties that are not necessarily exposed through the Microsoft OLE DB Provider for Jet to determine how to format the data.

Examples of these properties include the following: • General Date, Long Date, Long Time, Medium Time, Short Time, Medium Date, and Short Date are display formats for DateTime data type. • Hyperlink is a display format for Access Text data type. • True/False and On/Off both map to the Access Yes/No data type.

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List of the Most Common Data Type Mappings

The following table lists the most common data types that are used in Microsoft Access and how these data types relate to the Microsoft .NET Framework data types and to the OleDbType enumeration.

Access Type Name Database Data Type OLE DB Type .NET Framework Type Member Name Text VarWChar DBTYPE_WSTR System.String OleDbType.VarWChar Memo LongVarWChar DBTYPE_WSTR System.String OleDbType.LongVarWChar Number: Byte UnsignedTinyInt DBTYPE_UI1 System.Byte OleDbType.UnsignedTinyInt Yes/No Boolean DBTYPE_BOOL System.Boolean OleDbType.Boolean Date/Time DateTime DBTYPE_DATE System.DateTime OleDbType.Date Currency Decimal DBTYPE_NUMERIC System.Decimal OleDbType.Numeric Number: Decimal Decimal DBTYPE_NUMERIC System.Decimal OleDbType.Numeric Number: Double Double DBTYPE_R8 System.Double OleDbType.Double Autonumber (Replication ID) GUID DBTYPE_GUID System.Guid OleDbType.Guid Number: (Replication ID) GUID DBTYPE_GUID System.Guid OleDbType.Guid Autonumber (Long Integer) Integer DBTYPE_I4 System.Int32 OleDbType.Integer Number: (Long Integer) Integer DBTYPE_I4 System.Int32 OleDbType.Integer OLE Object LongVarBinary DBTYPE_BYTES Array of System.Byte OleDbType.LongVarBinary Number: Single Single DBTYPE_R4 System.Single OleDbType.Single Number: Integer SmallInt DBTYPE_I2 System.Int16 OleDbType.SmallInt Binary VarBinary* DBTYPE_BYTES Array of System.Byte OleDbType.Binary Hyperlink VarWChar DBTYPE_WSTR System.String OleDbType.VarWChar
* This data type is not available in the Access designer user interface. You must create this data type through code.

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REFERENCES

For more information about data types, visit the following MSDN Web sites:

OLE DB Provider for Microsoft Jet: Data Type Support
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/oledb/htm/oledbprovjet_data_type_support.asp (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/oledb/htm/oledbprovjet_data_type_support.asp)

OLE DB Provider for Microsoft Jet: Provider-Specific Properties in DBPROPSET_JETOLEDB_COLUMN
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/oledb/htm/oledbprovjet_provider_specific_properties_in_dbpropset_jetoledb_column.asp (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/oledb/htm/oledbprovjet_provider_specific_properties_in_dbpropset_jetoledb_column.asp)

OleDbType Enumeration
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfSystemDataOleDbOleDbTypeClassTopic.asp (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfSystemDataOleDbOleDbTypeClassTopic.asp)