Use CRecordSet separately

Generally, AppWizard automatically generates a CRecordset derived class in the database application, and associates the derived class with the table in a data source with the child window in the view. But sometimes this will affect the flexibility of the program. At this time, we can use the CRecordSet class separately. Using the CRecordSet class, we can execute SQL statements and read the data in the result set.

First, we need to include the header file afxdb. h. You can add # include to the stdafx. h file. In addition, when using CRecordset, there must be another CDatabase object. This object is used to manage data source connections. Then, you can generate a CRecordset object and run the SQL statement using BOOL CRecordset: Open (UINT nOpenType = AFX_DB_USE_DEFAULT_TYPE, LPCTSTR lpszSQL = NULL, DWORD dwOptions = none.

After successful execution, you can call the following function to scroll the cursor to read data.

MoveFirst	Move the cursor to the first record
MoveNext	Move the cursor to the next record
MovePrev	Move the cursor to the previous record
MoveLast	Move the cursor to the last record
IsBOF	Checks whether the cursor is on the first record
IsEOF	Checks whether the cursor is on the last record.
GetFieldValue	Data in the result

The code below is as follows:

/ *

Assuming CDatabase m_dbConn is a member variable

Suppose there is a table with the following SQL statement: CREATE TABLE table1 (loc_id not null)

* /

void CYourClass :: ConnectToDB ()

{//Connect to the database

BOOL fOK = m_dbConn.Open ("test");

TRACE ("connect fOK =% d
", m_dbConn);

}



void CYourClass :: Select ()

{// Execute the SELECT statement

CRecordset rec (& m_dbConn);

BOOL fOK = rec.Open (CRecordset :: forwardOnly, "select loc_id from table1 order by loc_id");

TRACE ("select fOK =% d
", fOK);

TRACE ("The number of columns returned is:% d
", rec.GetRowsetSize ());

CString szResult;

while (! rec.IsEOF ())

{

rec.GetFieldValue ((int) 0, szResult);

rec.MoveNext ();

TRACE ("fetch:% s
", szResult);

}

} 

In addition, CRecordset: GetFieldValue has many prototype types. You can obtain data by specifying the column position or field name:

Void GetFieldValue (LPCTSTRLpszName, CDBVariant &VarValue, ShortNFieldType= DEFAULT_FIELD_TYPE );

Void GetFieldValue (shortNIndex, CDBVariant &VarValue, ShortNFieldType= DEFAULT_FIELD_TYPE );

Void GetFieldValue (LPCTSTRLpszName, CString &StrValue);

Void GetFieldValue (shortNIndex, CString &StrValue);

If you use a variable of the CDBVariant type to obtain the result, you can get any type of result. The Data Types contained in the variable are recorded in the CDBVariant: m_dwType member variable. Based on the value of the variable, you can determine the data type and reference the corresponding member variables in the CDBVariant object.