ActiveX Data Objects

ADO is Microsofts universal data-access technology. This means that it can be used to obtain data from almost any source.
There are three versions of ADO in common use: 2.1, 2.5 and 2.6. Version 2.5 comes as standard with Windows 2000 or higher.
When using ADO you must have a reference to (Microsoft ActiveX Data Objects 2.5 Library) or the corresponding version in your Tools > References for that current Project
ADO doesn't actually access the data source directly but through a OLE DB.
Most OLE DB providers are specific to a single type of data source
Dynaset - a query based recordeset
You have the option to The default cachesize is 1 for ADO, which makes a trip for every row.

Objects

Out of the seven objects four of them (Connection, Command, Recordset and Parameter) can be created and manipulated independently of the others.
These objects can then be associated with others at run-time via the properties ActiveConnection and ActiveCommand.
Connection -
Command - Allows you to issue commands to the database
RecordSet - An array of rows
Record -
Stream - Not commonly used in Excel or Word applications

Field -
Property -
Parameter - Only needed when calling a stored procedure / function with parameters
Error - Allows you to retrieve information when an error occurs, SQLState, NativeError,Description

ADO will create objects even if you do not create them explicitly. For example a Recordset object always requires a connection object.
When a recordset is opened by passing a connection string, (and not a connection object), ADO creates an invisible connection object for you.
You should always explicitly create your connection object and re-use it where possible to avoid creating multiple connections to the same data source each time code is executed

Collections

Fields -
Properties -
Parameters -
Errors - Allows you to retrieve information when an error occurs

[Column] = Null

Extension Library

References
Microsoft ADO Ext. 2.5 for DDL and Security
Microsoft ADO Ext. 2.6 for DDL and Security
SS - include from References dialog

http://msdn.microsoft.com/en-us/library/aa139961(office.10).aspx
http://support.microsoft.com/kb/870962

Dim objCat as ADOX.Catalog 
Dim objTable As ADOX.Table 
Dim objIndex As ADOX.Index 

Set objCat = CreateObject("ADOX.Catalog")