ACC2: Using Microsoft Access Databases with Visual Basic 3.0

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Microsoft Visual Basic version 3.0 includes dynamic-link libraries (DLLs) that you can use to communicate with the Microsoft Access Jet database engine version 1.1 (Jet 1.1), used by Microsoft Access version 1.1. Jet 1.1 is also included with Visual Basic version 3.0 and can be freely distributed with applications created with it; there is no need to purchase Microsoft Access to obtain Jet 1.1.

You can use the DLLs in Visual Basic 3.0 to create Jet 1.1 applications. However, these DLLs cannot communicate with the Microsoft Access Jet database engine version 2.0 (Jet 2.0), used in Microsoft Access version 2.0. Visual Basic version 3.0 includes Jet 1.1 only; it does not include Jet 2.0. Jet 2.0 consists of the MSAJT200.DLL file, plus the various ISAM DLLs (PDX200.DLL, XBS200.DLL, and so on).

So that you can use Microsoft Access version 2.0 databases in Visual Basic version 3.0, a "compatibility layer," or series of files, was created to replace these DLLs. For example, the compatibility layer directly replaces the VBDB300.DLL file with a new version with the same name. When you use the compatibility layer in conjunction with Jet 2.0, you can use Microsoft Access version 2.0-created databases.

Note that it is not necessary to use the compatibility layer and Jet 2.0 combination to create database applications with Visual Basic 3.0; you can continue to use the DLLs included with Visual Basic 3.0 as before with no problem, as well as Jet 1.1 databases. Also, you can continue to use your current Jet 1.1 applications, even if you convert to Microsoft Access version 2.0, because it can still read Jet 1.1 databases. However, do not convert your Jet 1.1 databases to Jet 2.0 if you do not want to use the compatibility layer.

The compatibility layer is required only if you want to create applications that use Jet 2.0 and the following new features it contains:

• Data-definition queries
• Engine-level validation
• Programmatic access to security
• DAO (data access objects)
• Cascading deletes
• Temporary queries

The compatibility layer and Jet 2.0 are available in the Microsoft Access Developer's Toolkit (ADT) version 2.0. The compatibility layer only (without the Jet files) is available in the Microsoft Office Developer's Kit (ODK).