Note: This article is not originally original, it is from www.vckbase.com, if you have a charity, please contact me, I will delete. Thank you Author: North China University of Computer 2000 4 classes querw preparation: (1) the introduction of class ADO stdafx.h to add the header file. #import "c: / program files / compon files / system / ado / msado15.dll" /
NO_NAMESPACE /
Rename ("EOF", "AdoEOf") (2) Document / View class MFC program, then add AFXoleinit () in the initInstance () function to initialize the COM non-MFC environment: Coinitialize (NULL);
Couninitialize ();
(3) #import, you can use 3 smart pointers: _ConnectionPtr, _RecordSetPtr and _Commandptr, basically able to meet the database's operations through these three smart pointers. 1. Connect and close the database (1) Connection example: Connect Access Database M_PConnection.createInstance (__ uuidof (connection)); // Note: __ uuidof is used to get the GUID value of the rear expression.
Try
{
/ / Open the local Access library demo.mdb
m_pConnection-> open ("provider = microsoft.jet.oledb.4.0; datasource = demo.mdb",
"", ", admodeunknown;
}
Catch (_COM_ERROR E)
{
AFXMessageBox ("Database connection failed, confirming if the database demo.mdb is in the current path!");
Return False;
} (2), close // If the database connection is valid if (m_pconnection-> state)
m_pConnection-> close ();
M_PConnection = NULL;
(3), set connection time // Set connection time -------------------------------- pConnection-> PUT_CONNECTIONTIMEOUT (LONG (5)); 2. Open a result set (1) Open, first create a _recordsetptr instance, then call open () to get the execution result of a SQL statement _RecordSetPtr M_PRecordset;
M_PRecordSet.createInstance (__ uuidof (recordset);
/ / In ADO operation, it is necessary to use try ... catch () to capture error messages.
// Because it sometimes has some unexpected errors. Try
{
m_precordset-> Open ("Select * from demotable", // query all fields in the Demotable table
m_pconnection.getInterfacePtr (), // Get the IDSPATCH pointer to the library
AdoPENDYNAMIC,
AdlockOptimistic,
AdcmdText);
}
Catch (_COM_ERROR * E)
{
AfxMessageBox (E-> ErrorMessage ());
}
(2) Close the result set m_precordset-> close ();
3. Operate a result set (1), traverse (read) a), use precordset-> adoeof to determine if the database pointer has moved to the end of the result set; m_PRecordSet-> BOF determines if the first record appears in front: While (! m_precordset-> adoEof) {
Var = m_precordset-> getCollect ("name");
IF (var.vt! = vt_null)
Strname = (lpcstr) _BSTR_T (var);
VAR = m_precordset-> getCollect ("age");
IF (var.vt! = vt_null)
Strage = (LPCSTR) _BSTR_T (var);
M_accessList.Addstring (Strname "->" strage);
M_PRecordset-> MoveNext ();
}
b), there are two ways to obtain a field of a field.
Or m_precordset-> getCollect (_VARIANT_T (long (0));
The second is precordset-> get_collect ("colorn_name");
Or PrecordSet-> Get_Collect (long (index));
(2), add a), call m_precordset-> addnew (); b), call m_precordset-> PutCollect (); assign a value for each field C), call m_precordset-> Update (); confirmation (3), modify ( 4), delete a), move the record pointer to the record to be deleted, then call the delete (adAffectCurrent)
{
/ / Assume that the second record is deleted
M_PRecordset-> MoveFirst ();
M_PRecordset-> Move (1);
// starting from 0
M_PRecordset-> delete (AdaffectCurrent);
// Parameter adAffectCurrent To delete the current record
m_Precordset-> Update ();
}
Catch (_COM_ERROR * E)
{
AfxMessageBox (E-> ErrorMessage ());
}
4. Execute the SQL statement directly, in addition to the fact that most of the functions of the result set can be implemented directly (1), with _commandptr and _recordsetptr, _commandptr m_pcommand;
M_PCommand.createInstance (__ uuidof (command));
// Connect the library connection to it
M_PCOMMAND-> ActiveConnection = m_pConnection;
// SQL statement
m_pcommand-> commandtext = "select * from demotable";
/ / Execute SQL statement, return to record set
M_PRecordset = m_pcommand-> execute (null, null, adcmdtext); (2), directly using _ConnectionPTR execute SQL statement _RecordSetPtr connection15 :: execute (_BSTR_T CommandText,
Variant * Recordsaffected,
Long Options)
Where the CommandText is a command string, usually the SQL command.
The parameter recordsaffected is the number of rows affected after the operation is completed.
Parameter Options Represents the type of content in CommandText, options can be taken as one of the values: adcmdtext: indicates that CommandText is a text command.
AdcmdTable: Indicates that CommandText is a table name
AdcmdProc: Indicates that CommandText is a stored procedure
Adcmdunknown: Unknown
example:
_VARIANT_T RECORDSAFFECTED;
M_PCONNECTION-> Execute ("Update Users Set Old = OLD 1", & Recordsaffected, AdcmdText); 5. Call the stored procedure (1), using _commandptr_commandptr m_pcommand;
M_PCommand.createInstance (__ uuidof (command));
m_pcommand-> ActiveConnection = m_pconnection; // Connect the library connection
m_pcommand-> commandtext = "demo";
m_pcommand-> execute (null, null, adcmdstoredProc); (2), directly call directly _ConnectionPtr (see 4. (2)) 6. Traverse all table names in the database _ConnectionPtr M_PConnect;
_RecordSetPtr pset;
HRESULT HR;
Try
{
HR = m_pconnect.createInstance ("AdoDb.Connection");
En (ac))
{
CSTRING DD;
DD.FORMAT ("provider = microsoft.jet.Oledb.4.0; data source =% s", file);
HR = m_pconnect-> Open ((_ BSTR_T) DD, "", "", AdmodeunkNown;
Pset = m_pconnect-> OpenSchema (adschematables);
While (! (pset-> adoEof))
{
// Get the form
_BSTR_T TABLE_NAME = Pset-> Fields-> GetItem ("Table_Name") -> Value;
// Get the table type
_BSTR_T TABLE_TYPE = Pset-> Fields-> GetItem ("Table_TYPE") -> Value;
// Filter, only output the table name, other omissions
IF (Strcmp ((LPCSTR) Table_Type, "Table") == 0) {
CString TT;
TT.Format ("% s", (lpcstr) table_name);
AfxMessageBox (TT);
}
Pset-> MoveNext ();
}
Pset-> close ();
}
m_pconnect-> close ();
} catch (_COM_ERROR E) /// Capture Exception
{
CString ErrorMessage;
ErrorMessage.Format ("Connection Database Failed! RN Error Information:% S", E.ErrorMessage ());
AfXMessageBox; ErrorMessage;
Return -1;
} 7. Traversing all fields in a table Field * Field = NULL;
HRESULT HR;
Fields * Fields = NULL;
HR = m_precordset-> get_fields (& fields); // Get the field set and IF of the record set (SUCCEEDED (HR))
Fields-> Get_count (& colcount);
/ / Get the total number of fields in the field collection of records
For (i = 0; i
Item [i] -> get_name (& bstrcolname); // Get field name in record set //
Strcolname = BSTRCOLNAME;
Namefield = strcolname;
m_fieldslist.addstring (namefield);
}
En (ac))
Fields-> release (); // Release pointer
Attachment: 1, _variant_t (1), the value of these three pointers is not the data type directly supported by the MFC, and the _variant_t converts _variant_t (xx) can convert most types of variables into suitable Type Introduction: (2), _ variant_t var; _variant_t -> long: (long) var;
_variant_t -> cstring: cstring strval = (lpcstr) _BSTR_T (var);
CSTRING -> _VARIANT_T: _VARIANT_T (STRSQL); 2, BSTR wide string with cstring mutual conversion BSTR BSTR;
CString strsql;
CSTRING -> BSTR: BSTR = strsql.allocsystring ();
BSTR -> CSTRING: STRSQL = (LPCSTR) BSTR; 3, _BSTR_T and CSTRING Mutual conversion _BSTR_T BSTR;
CString strsql;
CSTRING -> _BSTR_T: BSTR = (_BSTR_T) strsql;
_BSTR_T -> CString: strsql = (lpcstr) BSTR; 4 ) Select * from my_table where datefield> # 2004-4-10 #
