It also makes your application run faster because it allows you to bypass Microsoft Jet’s middle layer. But ODBCDirect is more flexible, allowing you to run queries or stored procedures against the backend server and perform batch updates and asynchronous queries. There are some limitations in accessing ODBC data using Jet, although you can use it if you need to take advantage of a particular Jet feature. Jet and ISAM data use the Microsoft Jet object model however, with ODBC data, you can use either Microsoft Jet or ODBCDirect. Microsoft Jet (all databases that are created with the Microsoft Jet database engine).Keep in mind that all DAO objects are indexed beginning with zero.ĭAO lets you work with three database formats: When you create a new DAO object to be saved in the database, you have to append it to the appropriate collection using the collection’s Append method. Objects that represent the structure of the database are saved with the database. With DAO, objects you use to work with the data in the database are generally not saved but are created every time you need them. The Database object is the member of the Databases collection of the default Workspace object, which is a member of the Workspaces collection of the DBEngine object. It contains all other objects and collections.
The DBEngine is the highest-level object in the DAO object model. Names and descriptions of common DAO objects To understand DAO better, let’s look at the DAO objects in Figure A. Using DAO, you can create and modify the database structure create tables, queries, relationships, and indexes retrieve, add, update, and remove data implement security work with different file formats and link tables to other tables. But DAO doesn’t just let you access data-it also lets you control and manage local and remote databases in various formats. Let’s start with a look at DAO.ĭAO, which was created before RDO and ADO, is a set of objects that enables client applications to programmatically access data. We’ll also look at some cases where one is better suited for a specific task than another.
VISUAL BASIC DATA ACCESS FEATURES SERIES
In this series of articles, we will examine each of these options, noting their similarities and differences. When it comes to implementing a data access solution in your VB applications, you currently have three choices: Data Access Objects (DAO), Remote Data Objects (RDO), and ActiveX Data Objects (ADO). We kick off our series on data access with VB by looking at how you can implement DAO in your applications. DAO was the first, and it's still viable. There's more than one way to get at data from Visual Basic. Using DAO for data access in your VB apps
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