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DAO Recordset: Seeking and Finding

Visual Studio .NET 2003

This article explains how to use the Seek and Find member functions of class CDaoRecordset. Topics covered include:

These two mechanisms for locating records that meet certain criteria are used in different situations, as described in the following table.

Using Seek vs. Using Find

Criterion Seek Find
Use In Indexed table-type recordsets. Dynaset-type or snapshot-type recordsets.
Limitations Can't use on attached tables, but can use on installable ISAM databases. Can't use on a forward-only scrolling snapshot-type recordset. Use with ODBC-based recordsets can be inefficient.
Call Before Seek/Find SetCurrentIndex  
Call After Seek/Find Check Seek or Find return value Check Seek or Find return value

Seek and Find are not the only means of navigating in a recordset. You can also use:

  • Move, MoveFirst, MoveLast, MoveNext, and MovePrev
  • GetBookmark, SetBookmark
  • GetAbsolutePosition, SetAbsolutePosition
  • GetPercentPosition, SetPercentPosition

For more information, see each CDaoRecordset member function in the MFC Reference.

Using Seek

The CDaoRecordset::Seek member function lets you search for a record in a table-type recordset based on a table index. Two versions of the function provide for seeking based on:

  • Up to three specified keys, each of which represents a field that makes up part of the current index.
  • An array of keys, for indexes with four or more fields. Each key represents one of the fields. The array must contain at least one and no more than 13 keys.

In both versions, the search is based on a string containing a relational operator, such as "=" or ">=", in the lpszComparison parameter and the COleVariant value specified in the first key.

For example, suppose the comparison operator is "=" and the first key is the value "Microsoft" (the first key being a Company Name field). Using the first version of Seek, you would find the first record that has a Company Name of "Microsoft". The found record becomes the current record. The following code illustrates how to use Seek:

// rs is a table-type recordset
try
{
    // Set current index for recordset and 
    // save current position.
    rs.SetCurrentIndex( _T("PartNameIndex") );
    COleVariant varCurrentPos = rs.GetBookmark( );

    // variant used as a key in Seek
    COleVariant varKey (_T("Framis Lever"), VT_BSTRT);

    // Find first record whose Part Name 
    // field is "Framis Lever".
    if ( rs.Seek( _T("="), &varKey ) )
        // Return to the saved position
        rs.SetBookmark( varCurrentPos );
    else
        // Do something in response to Seek failure
}
catch( CDaoException* e )
{
    e->Delete( );
}

This code seeks the first record whose Part Name field (the first field in the PartNameIndex index) is "Framis Lever" (whatever a framis lever is).

For more information, see the Seek and SetCurrentIndex member functions in the MFC Reference. For related information about the underlying DAO functionality, see the following topics in DAO Help:

  • Seek Method
  • NoMatch Property
  • Index Object
  • Index Property

Using Find

The CDaoRecordset::Find member function and its relatives, FindNext, FindPrev, FindFirst, and FindLast, let you search for a record in a dynaset-type or snapshot-type recordset. The Find member functions search from a location and in a direction as shown in the following table.

The Find Family of Functions

Find operation Begin at Search direction
FindFirst Beginning of recordset End of recordset
FindLast End of recordset Beginning of recordset
FindNext Current record End of recordset
FindPrev Current record Beginning of recordset

The basic Find function takes two parameters:

  • The type of find: AFX_DAO_NEXT, AFX_DAO_PREV, AFX_DAO_FIRST, or AFX_DAO_LAST.
  • A filter — a string expression like the WHERE clause in an SQL statement (without the keyword), that specifies the criterion for finding. The expression can be compound, using AND, OR, and so on.

Find is a virtual function. This means you can, if necessary, override it to provide your own implementation. The other Find functions are all based on Find, so they use whatever functionality you provide in your override. You shouldn't normally need to override Find, however.

For details not discussed here about the Find member functions, see the individual functions, starting with Find. For related information about the underlying DAO functionality, see the topic "Positioning the Current Record Pointer with DAO" in DAO Help:

For example, suppose you have a dynaset-type recordset in which you want to find the first record with a State code of "NY":

// rs is a dynaset-type recordset previously opened
CString strCriteria = _T("STATE = 'NY'");
try
{
    if ( rs.FindFirst( strCriteria ) )
       // Do something with the found record
    rs.FindNext( strCriteria );
    // ...
}
catch( CDaoException* e )
{
    e->Delete( );
}

This code finds the first record that matches the criterion, then finds the next record that matches the criterion.

See Also

DAO Recordset | DAO: Where Is... | DAO Recordset | DAO Recordset: Recordset Navigation | DAO Recordset: Bookmarks and Record Positions

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