vcg01.htm

Visual C++与数据库的连接经典实例

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<FONT SIZE=5 COLOR="#FF0000"><B>Using Visual C++ as a Database Front End</B></FONT></CENTER></H3>

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<P>All of Microsoft's 32-bit mainstream Windows productivity applications and programming languages presently support or soon will accommodate the 32-bit Microsoft Jet 3.0 database engine. The Jet database engine is a software component that adheres to Microsoft's Component Object Model (COM) architecture. COM is Microsoft's infrastructure for creating code modules (called <I>objects</I>) that are independent of programming languages and computer platforms. COM defines a set of <I>interfaces</I> that applications must support; OLE 2+ is a high-level implementation of COM designed for sharing objects between Windows applications and for application programming. OLE 2+ defines its own set of interfaces to permit use of one program's objects by another program. As an example, applications that support VBA, such as Visual Basic 4.0, Access 95, Excel 95, and Project 95, communicate with the Jet 3.0 database engine (MSJT3032.DLL) through the Microsoft Jet 3.0 Data Access Object (DAO), DAO3032.DLL, an in-process OLE Automation server. (Access 95 also directly calls functions in MSJT3032.DLL). Thus, only a single copy of the Jet 3.0 DLLs is required in your \Windows\System folder; each application creates its own instance of Jet as needed. A similar approach is used to share other components, such as DAO, spell-checking, graphing, and VBA 2.0; the component files are located in subfolders of your \Windows\Program Files\Common Files\Microsoft Shared folder if you're running Windows 95.

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<P>Visual C++ is the wildcard in the desktop database deck. Visual C++ doesn't really have a native database structure. All four of the basic database types supported by Visual C++ are treated the same. Microsoft Access is simply the default database type. Visual C++ and its Access database engine, combined with Microsoft or third-party ODBC drivers, presently can connect to the relational database management systems (RDBMS) listed in Table 1.1.

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<FONT COLOR="#000080"><B>Table 1.1. Visual C++-compatible databases and file drivers.</B></FONT></CENTER>

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<I>Access Database </I><I>Engine Drivers</I>

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<I>Microsoft ODBC </I><I>Drivers</I>

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<I>Third-Part ODBC </I><I>Drivers</I>

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<TD VALIGN=top  BGCOLOR=#80FFFF ><FONT COLOR=#000080>

Access (.MDB)

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<TD VALIGN=top  BGCOLOR=#80FFFF ><FONT COLOR=#000080>

Microsoft SQL Server

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<TD VALIGN=top  BGCOLOR=#80FFFF ><FONT COLOR=#000080>

Digital Rdb

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<TD VALIGN=top  BGCOLOR=#80FFFF ><FONT COLOR=#000080>

Btrieve (.DAT)

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Oracle 6

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Gupta SQLBase

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<TD VALIGN=top  BGCOLOR=#80FFFF ><FONT COLOR=#000080>

dBASE III+ (.DBF, .NDX)

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<TD VALIGN=top  BGCOLOR=#80FFFF ><FONT COLOR=#000080>

Sybase SQL Server

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<TD VALIGN=top  BGCOLOR=#80FFFF ><FONT COLOR=#000080>

HP AllBase/SQL

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<TD VALIGN=top  BGCOLOR=#80FFFF ><FONT COLOR=#000080>

dBASE IV (.DBF, .MDX)

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Excel (.XLS)<SUP>*</SUP>

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HP Image/SQL

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FoxPro (.DBF, .CDX, .IDX)

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Text (.TXT)<SUP>*</SUP>

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IBM DB2, DB2/2

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Paradox (.DB, .PX)

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<TD VALIGN=top  BGCOLOR=#80FFFF ><FONT COLOR=#000080>

Access<SUP>*</SUP>

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IBM OS/2 DBM

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Btrieve<SUP>*</SUP>

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IBM SQL/DS

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<TD VALIGN=top  BGCOLOR=#80FFFF ><FONT COLOR=#000080>

dBASE III+<SUP>*</SUP>

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Informix

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dBASE IV<SUP>*</SUP>

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Ingres

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FoxPro 2.x<SUP>*</SUP>

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NCR Teradata

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Paradox<SUP>*</SUP>

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NetWare SQL

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