· Connection ¾ Opens a connection to a data source.
· Recordset ¾ Opens a cursor.
For a Connection object:
connection.Open ConnectionString, UserID, Password
For a Recordset object:
recordset.Open Source, ActiveConnection, CursorType, LockType, Options
The Open method syntax has these parts.
|
Part |
Description |
|
connection |
An object variable representing an existing Connection object. |
|
recordset |
An object variable representing an existing Recordset object. |
|
ConnectionString |
Optional. A String containing connection information. See the ConnectionString property for details on valid settings. |
|
UserID |
Optional. A String containing a user name to use when establishing the connection. |
|
Password |
Optional. A String containing a password to use when establishing the connection. |
|
Source |
Optional. A Variant that evaluates to a valid Command object variable name, an SQL statement, a table name, or a stored procedure call. |
|
ActiveConnection |
Optional. A Variant that evaluates to a valid Connection object variable name or a String containing a definition for a connection. |
|
CursorType |
Optional. A CursorTypeEnum value that determines the type of cursor that the provider should use when opening the Recordset. Can be one of the following constants: |
|
adOpenForwardOnly, 0 (Default) adOpenKeyset, 1 adOpenDynamic, 2 adOpenStatic, 3 | |
|
See the CursorType property for definitions of these settings. | |
|
LockType |
Optional. A LockTypeEnum value that determines what type of locking (concurrency) the provider should use when opening the Recordset. Can be one of the following constants: |
|
adLockReadOnly, 1 adLockPessimistic, 2 adLockOptimistic, 3 adLockBatchOptimistic, 4 | |
|
See the LockType property for definitions of these settings. | |
|
Options |
Optional. A CommandTypeEnum value that indicates how the provider should evaluate the Source argument if it represents something other than a Command object. Can be one of the following constants: |
|
adCmdText, 1 ¾ Evaluate Source as a textual definition of a command. adCmdTable, 2 ¾ Evaluate Source as a table name. adCmdStoredProc, 4 ¾ Evaluate Source as a stored procedure. adCmdUnknown, 8 ¾ The type of command in the Source argument is not known. | |
|
See the CommandType property for a more detailed explanation of these constants. |
Use the Open method on a Connection object or a Recordset object to activate the object for use. When you have concluded your operations over an open Connection object or in an open Recordset object, use the Close method to free any associated system resources. Closing an object does not remove it from memory; you may change its property settings and use the Open method to open it again later. To completely eliminate an object from memory, set the object variable to Nothing.
Using the Open method on a Connection object establishes the physical connection to a data source. After this method successfully completes, the connection is live and you can issue commands against it and process results.
Use the optional ConnectionString argument to specify a data source name (DSN) or a detailed connection string containing a series of argument = value statements separated by semicolons. If the argument contains an equal sign ("="), ADO assumes you are providing a connection string rather than a DSN. The ConnectionString property automatically inherits the value used for the ConnectionString argument. Therefore, you can either set the ConnectionString property of the Connection object before opening it, or use the ConnectionString argument to set or override the current connection parameters during the Open method call.
If you pass user and password information both in the ConnectionString argument and in the optional UserID and Password arguments, the results may be unpredictable; you should only pass such information in either the ConnectionString argument or the UserID and Password arguments.
Using the Open method on a Recordset object opens a cursor that represents records from a base table or the results of a query.
Use the optional Source argument to specify a data source using one of the following: a Command object variable, an SQL statement, a stored procedure, or a table name.
The ActiveConnection argument corresponds to the ActiveConnection property and specifies in which connection to open the Recordset object. If you pass a connection definition for this argument, ADO opens a new connection using the specified parameters.
For the arguments that correspond directly to properties of a Recordset object (Source, ActiveConnection, CursorType, and LockType), the relationship of the arguments to the properties is as follows:
· The property is read/write before the Recordset object is opened.
· The property settings are used unless you pass the corresponding arguments during the Open method. If you pass an argument, it overrides the corresponding property setting, and the property setting is updated with the argument value.
· After you open the Recordset object, these properties become read-only.
Note For Recordset objects whose Source property is set to a valid Command object, the ActiveConnection property is read-only, even if the Recordset object isn't open.
If you pass a Command object in the Source argument and also pass an ActiveConnection argument, an error occurs. The ActiveConnection property of the Command object must already be set to a valid Connection object or connection string.
If you pass something other than a Command object in the Source argument, you can use the Options argument to optimize evaluation of the Source argument. If the Options argument is not defined, you may experience diminished performance because ADO must make calls to the provider to determine if the argument is an SQL statement, a stored procedure, or a table name. If you know what Source type you're using, setting the Options argument instructs ADO to jump directly to the relevant code. If the Options argument does not match the Source type, an error occurs.
If the data source returns no records, the provider sets both the BOF and EOF properties to True, and the current record position is undefined. You can still add new data to this empty Recordset object if the cursor type allows it.