http://msdn.microsoft.com/zh-cn/library/t7yk8s5d(v=VS.90).aspx
CDBVariant没有基类。
CDBVariant对象表示用于MFC ODBC类的可变数据类型。CDBVariant与COleVariant类似;不过CDBVariant不使用OLE。CDBVariant允许存储值而不必关心值的数据类型。CDBVariant跟踪保存在一个联合中的当前值数据类型。
类CRecordset在三个成员函数中利用CDBVariant对象:GetFieldValue,GetBookmark和SetBookmark。例如GetFieldValue允许动态取一个列中的数据。因为运行时可能不知道列的数据类型,GetFieldValue使用一个CDBVariant对象来存储列的数据。
所需头文件:#include <afxdb.h>
Data Members
m_boolVal | Contains a value of type BOOL. |
m_chVal | Contains a value of type unsigned char. |
m_dblVal | Contains a value of type double. |
m_dwType | Contains the data type of the currently stored value. Type DWORD. |
m_fltVal | Contains a value of type float. |
m_iVal | Contains a value of type short. |
m_lVal | Contains a value of type long. |
m_pbinary | Contains a pointer to an object of type CLongBinary. |
m_pdate | Contains a pointer to an object of type TIMESTAMP_STRUCT. |
m_pstring | Contains a pointer to an object of type CString. |
m_pstringA | Stores a pointer to an ASCII CString object. |
m_pstringW | Stores a pointer to a wide CString object. |
Construction
Operations
Clear | Clears the CDBVariant object. |
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