Connections to SQL databases are implemented in two parts. The server owns the data. It may be either local to the client computer or it may be accessed over a local, wide area, or even an internet connection. A single server will handle requests from many users at a time. Most servers support the use of transactions, which insure that a set of changes made by a single user are visible to other users all at once.

The client program must connect to the server using instructions provided by the user and, usually, credentials in the form of a user name and password. Depending on the actual database, these instructions may be as simple as an ODBC alias or as complicated as a server name or address, TCP/IP port number, and a specific database to connect to.

The client program uses a special string value called a connection string to express the "directions" and "credentials" for connecting to any given database. We will discuss this connection string in more detail later. For now, it is enough to know that once you have selected a driver from the list of available drivers, a dialog is presented to help you build a connection string that can be used to reconnect to the database you choose later on.


Desktop Applications Only

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