The ADO Object Model - UserLand Software

The ADO Object Model - UserLand Software

ADO & Recordsets ADO Description & History ActiveX Data Objects History 1991 ODBC Data Access Objects (DAO) for VB developers (JET) Remote Data Object (RDO) SQL, Oracle, etc (ODBC) ODBCDirect utilizing RDO

OLE DB ADO is a wrapper for OLE DB High level, object oriented interface Intended to replace DAO and RDO. The ADO Object Model Connection Command Parameters Parameter

Error Errors Recordset Fields The Connection Object Represents link to the data source Directly

execute statements against source Manage transactions Expose events to notify of completed tasks Provides Error object/collection ADO does not require Connection object, but it is highly beneficial to declare explicitly. The Recordset Object Supports data paging

Disconnected recordsets Filtering Sorting Storing multiple data sets in a single object Recordsets and ASP VBScript Creating a Connection object Recordset samples Executing action queries Cursors

Locks Connection Object Microsoft Access Example Microsoft SQL Server Example Recordset Example http://www.jeonglee.com/ado Cursors Determines

how you can move through the recordset Determines properties and methods made available through recordset object Can only be specified upon opening a recordset Specify it using .CursorType property in recordset object or as the third parameter using .Open method Performance considerations Cursors Adopenforwardonly

(Value 0) Default The data is alive but you can only move forward. Cannot move backward or to specific record Adopenkeyset The (Value 1) data is alive and any record read will be the most recent data. Adopendynamic

(Value 2) The data is alive and additions will be noticed. Accurate recordcount. Adopenstatic The (Value 3) data is dead. It is like a snapshot of the data. Accurate recordcount.

Locks Data modification and concurrency Choice of locking depends on business rules Locks AdLockReadOnly (Value 1) Default Read-only

recordset, no locking provided since data cannot be updated. AdLockPessimistic Attempts to lock record once editing starts. AdLockOptimistic Only (Value 2) (Value 3)

locks the record when .Update method is used. AdLockBatchOptimistic Locks (Value 4) are issued when .UpdateBatch method is used.

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