Connection object
Attributes
Attribute name data type and purpose
Attributes can read and write long types, with two constants and specify whether to use retention transactions (Retainning Transactions). Constant ADXACTCommitRetaining indicates a new transaction when calling a committrans method; constant adxactabortretaning means that a new transaction is initiated when calling the RollbackTrans method. The default is 0, indicating that it does not use the retained transaction.
CommandTimeout reads the long type to specify the time you must wait until the Execute call for a relevant Command object. The default is 30 seconds.
Connectionstring Read Write String Type, provides specific information required to provide a data provider or service provider to open to a data source
ConnectionTIMEOUT can read and write long types, specify that the time you must wait for a failure of a failed Connection.Open method call, the default is 15 seconds.
CursorLocation Reads LONG Type, determined to use the client (ADUSECLIENT) cursor engine, or use the server-side cursor engine. The default is aduseserver.
DEFAULTDATABASE reads and writes String type. If you do not specify a database name in ConnectString, you will use the name specified here. For SQL Server, its value is usually PUBS.
IsolationLevel reads the long type, specifying and other parallel transactions interacting behavior or transactions. See ISOLATIONLEVEL constant
Mode long type, specify read and write permissions to Connection. See MODE constant
Provider reads and writes String type, if you do not specify an OLE DB data or service provider's name in Connectionstring, use the name specified at this time. The default is MSDasql (Microsoft Ole DB Provider for ODBC).
State Readable LONG Type, specifying the connection is in an open state, or is in a closed state or an intermediate state. See State constant
Version read-only String type, returns the ADO version number.
Note: Most of the readable and writable properties listed above, only when the connection is in turn off, it is written.
Only when the user uses the BeGintrans ... CommitTrans ... RollbackTrans method defines the specified for the degree of transaction isolation. If there are multiple database users to execute transactions at the same time, the application must specify how to respond to other transactions in the run.
method
Method use
BeGintrans initializes a transaction; there must be COMMITTRANS and / or ROLLBACKTRANS
Close Close connection
CommitTrans submits a transaction to complete the permanent change of the data source (Begintrans method must be called before use)
The EXECUTE SELECT SQL statement returns a Forward-Only Recordset object, and it is also used to perform those who do not return a Recordset statement, such as INSERT, UPDATE, DELETE query, or DDL statement.
Open uses a connection string to open a connection
OpenSchema returns a RECORDSET object to provide the data source structure information (Metadata)
RollbackTrans cancels a transaction, restores a temporary change for the data source (Begintrans method must be called before use)
Note: Three ways that execute, Open, and OpenSchema can accept variable parameters. Execute's grammar is: cnnname.execute strcommand, [lngrowsaffected [, lngoptions]]
The value of strcommand can be a SQL statement, a table name, and a stored procedure name, or any string that the data provider can accept. In order to improve performance, it is best to specify a suitable value for the LNGOptions parameter (see the constant for the LNGOptions parameter) to enable the provider to explain the statement without determining its type. Optional parameters LNGROWSAFFECTED will return the number of INSERT, UPDATE, or DELETE queries. These queries returns an off Recordset object. A SELECT query will return the LNGROWSAFFECTED value of 0 and return Forward-Only RecordSet with a row or multi-line content.
event
Event name trigger time
BegintransComplete Begintrans method is executed.
Private sub cNNNAME_BEGINTRANSCOMPLET (Byval TransactionLevel As Long, Byval Perror As AdoDb.Error, Adstatus As Adodb.EventStatusenum, BYVAL PCONNECTION As adoDb.connection)
After the committranscomplete committrans method
Private sub connection1_commitTranscomplete (Byval Perror As AdoDb.Error, Adstatus As Adod.EventStatusenum, ByVal PConnection As Adodb.Connection)
After the ConnectComplete successfully established the connection to the data source
Private sub connection1_connectcomplete (byval perror as adoDb.error, adstatus as adodb.eventstatusenum, byval pconnection as adoDb.connection)
DiSConnect Connection is turned off
Private sub connection1_disconnect (adstatus as adodb.eventStatusenum, byval pconnection as adodb.connection)
EXECUTECOMPLETE When constant Connection.execute or Command.execute
Private Sub Connection1_ExecuteComplete (ByVal RecordsAffected As Long, ByVal pError As ADODB.Error, adStatus As ADODB.EventStatusEnum, ByVal pCommand As ADODB.Command, ByVal pRecordset As ADODB.Recordset, ByVal pConnection As ADODB.Connection)
InfubusSage An error object is added to the AdoDb.Connectio.Error collection
Private sub connection1_infomessage (byval perror as adoDb.error, adstatus as adodb.eventstatusenum, byval pConnection as adodb.connection)
RollbackTranscomplete RollbackTransComplete RollbackTransComplete RollbackTransComplete RollbackTransComplete
Private sub connection1_rollbacktranscomplete (byval perror as adodb.error, adstatus as adodb.EventStatusenum, byval pConnection as adoDb.connection) WillConnect is about to call Connection.Open methods
Private sub connection1_willconnect (Connectionstring As String, Userid As String, Password As String, Options as long, adstatus as adodb.eventStatusenum, Byval PConnection As adoDb.connection)
Willexecute is about to call Connection.execute or Command.execute method
Private Sub Connection1_WillExecute (Source As String, CursorType As ADODB.CursorTypeEnum, LockType As ADODB.LockTypeEnum, Options As Long, adStatus As ADODB.EventStatusEnum, ByVal pCommand As ADODB.Command, ByVal pRecordset As ADODB.Recordset, ByVal pConnection As ADODB.Connection )
Note: The name and meaning of the constant used in the AdStatus parameters are detailed in the constant used by Adstatus.
constant
IsolationLevel constant
Constant meaning
ADXACTCURSORSTABILITY only allows you to read other transactions (default)
ADXACTBROWSE allows you to read other transactions
The ADXACTCHAOS This business does not overwrite changes made by other levels of isolation.
ADXACTISOLATED all the transactions
ADXACTREADCOMMITTED is equivalent to ADXACTCURSORSTABILITY
ADXACTREADUNCOMMITTED is equivalent to ADXACTBROWSE
ADXACTREPEATABLEREAD prohibits reading other transactions
ADXACTSERIALIZABLE is equivalent to ADXACTISOLATED
ADXACTUNSPECIFIED cannot determine the degree of transaction isolation of the provider
Mode constant
Constant meaning
AdmodeunkNown does not specify the connection permission of the data source (default)
The AdmodeRead connection is read-only.
AdmodeReadwrite connection is readable
Admodesharedenynne does not reject other users' read and write access (the default value of Jet OLE DB Provider)
AdmodesharednyRead rejects other users to open a read connection to the data source
AdmodesharedenYwrite Rejects other users to open a write connection to the data source
AdmodesharexClusive opens the data source exclusive way
The AdmodeWrite connection is only written.
State constant
Constant meaning
AdStateClosed Connection is off (default)
AdStateConnecting is connected to the status of the data source
The Execute method of the AdstateExecuting Connection or Command object has been called
AdstateFetching Return (ROW) to the Recordset object
AdStateOpen Connection (or other object) is open (activity)
Constant for LNGOption parameters in the execute method
Command type constant meaning
AdcmDunkNown Command Type Unexpected (Default)
AdcmdStoredProc Command is a stored procedure name
AdcmdTable Command is a table name that can generate internal Select * from tablename queries
AdcmdtableDirect Command is a table name that can get the contents of the content directly from the table.
ADCMDTEXT COMMAND is a SQL statement
ADODB event processes the constant used by subsection parameters Adstatus
Constant meaning
AdstatusCancel operation is canceled by the user
AdstusCnatdeny operations cannot reject other users access to data sources
AdStatuserRorsoccurred operations cause errors and have been delivered to the Erroors collection
Adstatusok operation success
An unpredited event is activated during the AdstatusnuNTedEvent operation
