14.2 Initialization

14.2.5 Database connection and disconnection

Once the database type has been initialized a connection can be established by callingconnect. A call toconnect sets*default-database* to the database instance which represents the connection. All the other database functions described take a:database argument that can be either a database or a database name, and which defaults to*default-database*.

*default-database*

Variable

: Specifies the default database to be used for database operations.

connected-databases

Function

: Returns a list of database connection instances.

connect

Function

connect connection-spec &key if-exists database-type

: Opens a connection to a database of database-type. The argument connection-spec depends on the type of the connected database. For databases of type:odbc, the connection specification is a string of the format

"datasource-name/username/password"

where datasource-name is the name of a suitable datasource, and username and password are a valid username and password. If the datasource does not require a username and password they can be omitted.

Theconnect function sets*default-database* to an instance of the database opened and returns that instance. The argument if-exists modifies the behavior ofconnect as follows:

:new: Makes a new connection even if connections to the same database already exist.
:warn-new: Makes a new connection but warns about existing connections.
:error: Makes a new connection but signals an error for existing connections.
:warn-old: Selects the old connection if one exists (and warns) or makes a new one.
:old: Selects the old connection if one exists or makes a new one.

*connect-if-exists*

Variable

: Default value for the:if-exists variable of theconnect function. See the connect description for the possible values. Initial value is:error.

disconnect

Function

disconnect &key database

: Closes the connection to database. Resets*default-database* if that database was disconnected and only one other connection exists.

database-name

Function

database-name database

: Returns the database connection string.

find-database

Function

find-database database &optional errorp

: Returns a database given its name or itself. If database is not found among the connected databases and errorp is non-nil thenfind-database signals an error, otherwise it returnsnil. By default, errorp ist.

status

Function

status &optional full

: Returns status information for the connected databases and initialized database types. By default, full isnil. Ift, more detailed information is returned.