db_accessor
Groups db_column attributes that participate in IAccessor-based binding.
[ db_accessor(
num,
auto
) ]
Parameters
num
Specifies the accessor number (a zero-based integer index). You must specify accessor numbers in increasing order, using integers or defined values.auto
A Boolean value that specifies whether the accessor is automatically retrieved (TRUE) or not retrieved (FALSE).
Remarks
db_accessor defines the underlying OLE DB accessor for subsequent db_column and db_param attributes within the same class or function. db_accessor is usable at member level and is used to group db_column attributes that participate in OLE DB IAccessor-based binding. It is used in conjunction with either the db_table or db_command attributes. Calling this attribute is similar to calling the BEGIN_ACCESSOR and END_ACCESSOR macros.
db_accessor generates a rowset and binds it to the corresponding accessor maps. If you do not call db_accessor, accessor 0 will automatically be generated, and all column bindings will be mapped to this accessor block.
db_accessor groups database column bindings into one or more accessors. For a discussion of the scenarios in which you need to use multiple accessors, see Using Multiple Accessors on a Rowset. Also see "User Record Support for Multiple Accessors" in User Records.
When the consumer attribute provider applies this attribute to a class, the compiler will rename the class to _YourClassNameAccessor, where YourClassName is the name you gave the class, and the compiler will also create a class called YourClassName, which derives from _YourClassNameAccessor. In Class View, you will see both classes.
Example
The following example uses db_accessor to group columns in the Orders table from the Northwind database into two accessors. Accessor 0 is an automatic accessor, and accessor 1 is not.
// cpp_attr_ref_db_accessor.cpp
// compile with: /LD /link /OPT:NOREF
#define _ATL_ATTRIBUTES
#include <atlbase.h>
#include <atldbcli.h>
[ db_command(L"SELECT LastName, FirstName FROM Orders") ]
class CEmployees {
public:
[ db_accessor(0, TRUE) ];
[ db_column("1") ] LONG m_OrderID;
[ db_column("2") ] TCHAR m_CustomerID[6];
[ db_column("4") ] DBTIMESTAMP m_OrderDate;
[ db_accessor(1, FALSE) ];
[ db_column("8") ] CURRENCY m_Freight;
};
Requirements
Attribute Context
Applies to |
Attribute blocks |
Repeatable |
No |
Required attributes |
None |
Invalid attributes |
None |
For more information about the attribute contexts, see Attribute Contexts.