DevGuru ADO Connection Object



			OBJECT: Connection Connection The ADO Connection object provides the means to obtain an open connection to a data source. Through this open connection, you can access and manipulate a database. In order to query a database, you do not need to explicitly create a Connection object. A connection can be made by passing a connection string via a Command or Recordset object. However, such a connection is only good for that specific, single query. If you desire to access a data source multiple times, it is far more efficient to establish a connection using the Connection object. In a similar vein, you can pass a query string using the Execute method of the Connection object. However, a Connection object query lacks the superior functionality of a Command object query. Only the Connection and Recordset objects have events. Note that only the Visual Basic, Visual C++, and Visual J++ languages can handle these events. You cannot handle an event using the VBScript or JScript scripting languages. Carl Prothman of Able Consulting, Inc. maintains a web site containing sample ADO connection strings for ODBC DSN, ODBC DSN-Less, OLE DB Provider, and MS Remote. The Guru highly recommends you visit this extremely useful site. PROPERTIES Attributes Property Sets or returns a long value defining the characteristics of a Connection object. Syntax: connectionobject. Attributes CommandTimeout Property Sets the number of seconds to wait while attempting an Execute method call before terminating the attempt and generating an error message. Syntax: connectionobject. CommandTimeout ConnectionString Property Sets or returns a string value that contains the details used to create a connection to a data source. Syntax: connectionobject. ConnectionString ConnectionTimeout Property Sets the number of seconds to wait while attempting to create a connection before terminating the attempt and generating an error message. Syntax: connectionobject. ConnectionTimeout CursorLocation Property Sets or returns a long value used to select between various cursor libraries accessible through the provider. Syntax: connectionobject. CursorLocation DefaultDatabase Property Sets or returns a string value that is the default name of the database available from the provider for a Connection object. Syntax: connectionobject. DefaultDatabase IsolationLevel Property Sets or returns the transaction isolation level (the IsolationLevelEnum value) of a Connection object. Syntax: connectionobject. IsolationLevel Mode Property Sets or returns the provider access permission (the ConnectModeEnum value) for a Connection object. Syntax: connectionobject. Mode Provider Property Sets or returns the string value that is the provider name. Syntax: connectionobject. Provider State Property Returns a long value (the ObjectStateEnum value) describing if the connection is open or closed. Syntax: connectionobject. State Version Property Returns a string value that is the ADO version number. Syntax: connectionobject. Version COLLECTIONS Errors Collection A collection of Error objects that were generated by the failure of a connection operation. Properties Collection A collection of Property objects. Each Property object contains a provider-specific property. METHODS BeginTrans Method Begins a new transaction and returns a long value indicating the number of nested transactions. Syntax: connectionobject. BeginTrans Cancel Method Cancels the execution of a pending Execute or Open call. Syntax: connectionobject.Cancel Close Method Closes a connection. Syntax: connectionobject.Close CommitTrans Method Saves any changes and ends the current transaction. It can also be set to automatically start a new transaction. Syntax: connectionobject.CommitTrans Execute Method Executes the query, SQL statement, stored procedure, or provider-specific text. Syntax: connectionobject.Execute (CommandText, RecordsAffected, Options) Open Method Opens a physical connection to a data source. Syntax: connectionobject.Open (ConnectionString, UserID, Password, Options) OpenSchema Method Returns descriptive schema information from the provider about the data source. Syntax: connectionobject.OpenSchema (QueryType, Criteria, SchemaID) RollbackTrans Method Cancels any changes that have occurred during the current transaction and then ends the transaction. It can also be set to automatically start a new transaction. Syntax: connectionobject.RollbackTrans EVENTS BeginTransComplete Event After a BeginTrans operation has finished executing, you can call this event to trigger other operations. Syntax: BeginTransComplete (TransactionLevel, pError, pConnection) CommitTransComplete Event After a CommitTrans operation has finished executing, you can call this event to trigger other operations. Syntax: CommitTransComplete (pError, adStatus, pConnection) ConnectComplete Event After a connection has started, you can call this event to provide information on the success of the connection. Syntax: ConnectComplete (pError, adStatus, pConnection) Disconnect Event After a disconnection, you can call this event to provide information on the success of the disconnection. Syntax: Disconnect Event (adStatus, pConnection) ExecuteComplete Event After a command has finished executing, you can call this event to provide information on the success of the command and the number of records affected. Syntax: ExecuteComplete Event (RecordsAffected, pError, adStatus, pCommand, pRecordset, pConnection) InfoMessage Event This event is called if a warning occurs during a ConnectionEvent operation. Syntax: InfoMessage (pError, adStatus, pConnection) RollbackTransComplete Event After a RollbackTrans operation has finished executing, you can call this event to trigger other operations. Syntax: RollbackTransComplete (TransactionLevel, pError, MessageStatus, pConnection) WillConnect Event This event can be called before the connection starts. You can change any of the parameters and even cancel the connection. Syntax: WillConnect (ConnectingString, UserID, Password, Options, adStatus, pConnection) WillExecute Event This event is called before a pending command is executed. It allows you to change the execution parameters. Syntax: WillExecute Event (Source, CursorType, LockType, Options, adStatus, pCommand, pRecordset, pConnection)