Seeking partial strings in CDaoRecordset class
Sometimes while searching for something in CDaoRecordset object we often use Seek() function. But the problem with the DAO is, it reports FALSE when search is made for partial string. For example suppose there is record "Sharad" in the FirstName field of table and it is indexed. If search is made for some prefix only the return value is FALSE as shown here:
COleVariant var("Sha");
The whole point is very relevant when we want to quickly navigate through record set as the user types the key strokes for the item he is searching.
To get around this I have implemented a function called PartialSeek( const char * szStr , const char * szFieldName ) as member of CDaoRecordset. To use this the accompanying source code of this function should be added to your CDaoRecordset derived class :
class CMyRecordset :public CDaoRecordset
{
public:
BOOL PartialSeek(const char * szStr , const char * szFieldName ) ;
} ;
BOOL CMyRecordset::PartialSeek( const char * szStr , const char * szFieldName )
{
int nSeekResult ;
int nStrCmp;
int nLen ;
COleVariant Var(szStr , VT_BSTRT );
COleVariant Extract ;
COleVariant varBookMark ;
nLen = strlen(szStr);
varBookMark = GetBookmark();
nSeekResult = Seek("<", &Var);
MoveNext();
if (IsBOF() ||IsEOF())
{
SetBookmark(varBookMark);
return 0 ;
}
GetFieldValue( szFieldName , Extract) ;
nStrCmp = _strnicmp(szStr, (const char *)Extract.bstrVal, nLen );
if ( nStrCmp == 0)
{
return TRUE ;
}
else
{
SetBookmark(varBookMark);
return FALSE ;
}
}
How to call function:
Suppose the field is FirstName search key is "Sha"
We should make call like this: PartialSeek("Sha" , "FirstName") ;
Prerequisite
(1) This works only with text type of fields:
(2) The field must be indexed.
(3) Before using this function the index should be switched to the field we are looking for, by making a call to SetCurrentIndex() ;
Date Last Updated: April 4, 1999
