Sunday, January 4, 2009


Hi all, Hope this post will help for the DB beginners. :)
Back in the old days, database connectivity was difficult. Everybody had their own database formats, and developers had to know a low level API for each database they wished to develop for. There was a push for a universal API, an API which would work for numerous data stores. It was about this time that ODBC, or Open Database Connectivity, which was an early attempt at creating this universal API. A number of databases conformed to this standard, and became known as ODBC-compliant databases. ODBC-compliant databases consist of Access, MS-SQL Server, Oracle, Informix, etc.

ODBC is Open Data Base Connectivity, which is a connection method to data sources and other things. It requires that you set up a data source, or what's called a DSN using an SQL driver or other driver if connecting to other database types. Most database systems support ODBC

Well, ODBC wasn't perfect. It still contained a lot of low-level calls, and was difficult to develop with. Developers had to focus more on low-level communications with the database, as opposed to being able to concentrate on getting the data they needed and using it how they saw fit. Along came Microsoft's solution: DAO, or Data Access Objects.

.OLE is Object Linking and Embedding. OLEDB is partly distinguished from OLE itself, now called "automation". OLEDB is the successor to ODBC, a set of software components that allow a "front end" such as GUI based on VB, C++, Access or whatever to connect with a back end such as SQL Server, Oracle, DB2, mySQL etal. In many cases the OLEDB components offer much better performance than the older ODBC.OLEDB is a different type of data provider that came about with MS's Universal Data Access in 1996 and does not require that you set up a DSN. It is commonly used when building VB apps and is closely tied to ADO. It works with COM, and DCOM as of SQL 7.0.

OLEDB sits between the ODBC layer and the application. With your ASP pages, ADO is the "application" that sits above OLEDB. Your ADO calls are first sent to OLEDB, which are then sent to the ODBC layer. You can connect directly to the OLEDB layer, though, and if you do so, you'll see an increase in performance for server-side cursors (the default cursor type for recordsets, and the most common type of cursor used).

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