CDatabase

CDatabase對象表示到數據源的連線，通過它可以運算元據源。

基本介紹

• 中文名：數據源的連線
• 外文名：CDatabase
• 功能：數據源操作
• 數據源：MicrosoftSQL Server
• 輔助：OpenEx成員函式
• 所需頭檔案：#include <afxdb.h>

CDatabase詳解

數據源是位於一些資料庫管理系統（DBMS）的數據的指定實例，包括MicrosoftSQLServer，MicrosoftAccess，BorlanddBASE和xBASE。在套用中可以同時使一個或多個CDatabase對象活動。

注意：

如果在處理數據訪問對象（DAO）類而不是開放資料庫連線（ODBC）類，可使用類CDaoDatabase。有關的更多信息，請參閱在線上文檔“Visual C++程式設計師指南”中的“資料庫主題（通用）”與“DAO和MFC”。

為使用CDatabase，構造一個CDatabase對象並調用它的OpenEx成員函式。這打開了一個連線。在接著構造CRecordset對象以操縱連線的數據源時，向CDatabase對象傳遞記錄集構造程式指針。完成使用連線時調用Close成員函式並銷毀CDatabase對象。Close關閉以前沒有關閉的任何記錄集。

Data Members

m_hdbc

Open Database Connectivity (ODBC) connection handle to a data source. Type HDBC.

Construction

CDatabase	Constructs a CDatabase object. You must initialize the object by calling OpenEx or Open.
Open	Establishes a connection to a data source (through an ODBC driver).
OpenEx	Establishes a connection to a data source (through an ODBC driver).
Close	Closes the data source connection.

Database Attributes

GetConnect	Returns the ODBC connect string used to connect the CDatabase object to a data source.
IsOpen	Returns nonzero if the CDatabase object is currently connected to a data source.
GetDatabaseName	Returns the name of the database currently in use.
CanUpdate	Returns nonzero if the CDatabase object is updatable (not read-only).
CanTransact	Returns nonzero if the data source supports transactions.
SetLoginTimeout	Sets the number of seconds after which a data source connection attempt will time out.
SetQueryTimeout	Sets the number of seconds after which database query operations will time out. Affects all subsequent recordset Open, AddNew, Edit, and Delete calls.
GetBookmarkPersistence	Identifies the operations through which bookmarks persist on recordset objects.
GetCursorCommitBehavior	Identifies the effect of committing a transaction on an open recordset object.
GetCursorRollbackBehavior	Identifies the effect of rolling back a transaction on an open recordset object.

Database Operations

BeginTrans	Starts a “transaction” — a series of reversible calls to the AddNew, Edit, Delete, and Update member functions of class CRecordset — on the connected data source. The data source must support transactions for BeginTrans to have any effect.
BindParameters	Allows you to bind parameters before calling CDatabase::ExecuteSQL.
CommitTrans	Completes a transaction begun by BeginTrans. Commands in the transaction that alter the data source are carried out.
Rollback	Reverses changes made during the current transaction. The data source returns to its previous state, as defined at the BeginTrans call, unaltered.
Cancel	Cancels an asynchronous operation or a process from a second thread.
ExecuteSQL	Executes an SQL statement. No data records are returned.

所需頭檔案：#include <afxdb.h>

Database Overridables

OnSetOptions

Called by the framework to set standard connection options. The default implementation sets the query timeout value. You can establish these options ahead of time by calling SetQueryTimeout.