CDatabase详解

Data Member(Database Attribute Database Operation Database Overridable)

CDatabase详解

CDatabase对象表示到数据源的连接，通过它可以操作数据源。数据源是位于一些数据库管理系统（DBMS）的数据的指定实例，包括MicrosoftSQL Server，Microsoft Access，Borland dBASE和xBASE。在应用中可以同时使一个或多个CDatabase对象活动。

注意：

如果在处理数据访问对象（DAO）类而不是开放数据库连接（ODBC）类，可使用类CDaoDatabase。有关的更多信息，请参阅联机文档“Visual C++程序员指南”中的“数据库主题（通用）”与“DAO和MFC”。

为使用CDatabase，构造一个CDatabase对象并调用它的OpenEx成员函数。这打开了一个连接。在接着构造CRecordset对象以操纵连接的数据源时，向CDatabase对象传递记录集构造程序指针。完成使用连接时调用Close成员函数并销毁CDatabase对象。Close关闭以前没有关闭的任何记录集。

Data Member

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 Attribute

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 Operation

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.所需头文件：#include <afxdb.h>

Database Overridable

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.