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C++Builder Database Architecture
To avoid logging in each time the database is opened, set the KeepConnection property
to true.
If the LoginPrompt property is set to true, the user will be prompted for login information
when connecting to the database server. You can override this using the OnLogin event
(detailed in the following section, “Tasks”).
Set the TransIsolation property to specify the transaction isolation level (TIL) to establish on
the database server. The TIL you select affects both your ability to see transactions originated
by other users and their ability to see transactions you initiate.
Tasks
Your application must include a Database component to do any of the following:
■ Establish a permanent database connection
■ Establish local, application-specific database aliases
■ Change server login parameters
■ Manipulate server-based transaction-control mechanisms
Establishing Database Connections
C++Builder applications connect to SQL servers using the SQL Links drivers for the Borland
Database Engine. These drivers provide access to the InterBase, Sybase, Oracle, and
Microsoft DBMSs.
Typically, you’ll use the Database Explorer or the BDE Configuration utility to construct
database aliases through which your application will connect to these back-end servers. A
BDE alias is no more than a named parameter list—a set of connection information that the
BDE uses to connect you to your database. Once you’ve set up an alias, it appears in the
DatabaseName property list of TDataset components such as TTable and TQuery. You can
override the defaults provided by a BDE alias by editing TDatabase’s Params property. The
settings you make in Params override the parameters that are embedded in the alias definition.
Retaining Database Connections
You set the KeepConnection property of a TDatabase component to true to cause database
connections to be retained even when no TDatasets are open. This is necessary if you want
to avoid having to log in the next time a connection is needed.
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