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438 Day 12
Table 12.6. TDatabase key methods.
Method Function
Open Explicitly opens a database connection.
Close Explicitly close a database connection.
Table 12.7. TDatabase key events.
Event Catalyst
OnLogin Occurs when a SQL TDatabase is opened and LoginPrompt is true.
Key Elements
You use the DatabaseName property to define an application-specific, or local, BDE alias.
Once you’ve specified a name here (it can be the same as the component’s Name property, if
you like), you’ll see it “published” in the drop-down DatabaseName property list of TDataset
components like TTable and TQuery. You can then select it from those lists to link the
associated TDataset component with your Tdatabase.
AliasName specifies the BDE alias you want this TDatabase to use. It refers to an alias you’ve
already defined using the BDE Configuration utility and uses it to get default settings. Note
that this property and the DriverName property are mutually exclusive. Setting one automatically
clears the other.
If you elect not to set AliasName, use the DriverName property to identify a BDE driver that
you want to use instead. This can include the STANDARD driver for local tables (dBASE
and Paradox), or the INTERBASE, SYBASE, ORACLE, or MSSQL drivers for SQL
database servers. As mentioned previously, the DriverName property and the AliasName
property are mutually exclusive.
Toggling the Connected property opens and closes the database connection. You can set it to
true in the C++Builder Object Inspector to open a database connection while you’re
designing. If you open a TDataset that refers to your TDatabase, the TDatabase will
automatically be opened. If you close a TDatabase that has associated TDatasets, you’ll close
them as well.
TIP
Note that if you define an application-specific alias, the form or data
module that contains the associated TDatabase must be currently loaded
in order for you to open TDatasets that reference it.