About Opening Database Connections with ADO

You can use any of these three types of ADO objects to establish a connection to a database:

• Command object. This object opens a connection into the database. With the command object, you can execute a simple text query, query a database table, or run a stored procedure. All database access from the CML/LitCrit application's COM components is through stored procedures, so these components always instantiate a command object first.
• Connection object. This object also opens a connection into the database. You can run queries after instantiating a connection object, but not stored procedures. You can also retrieve data with a connection object by executing queries, but they do not return recordsets.
• Recordset object. If you have to open more than one recordset, open a connection object first and then pass this connection object string as a parameter when you use the recordset object. If you want to instantiate just one recordset object, you don't need to open a connection object first; just pass the DSN as a parameter of the recordset object.

The CML/LitCrit application uses a single recordset object when it needs to execute a single action in the database.

You will need to use more then one recordset object if you need to access data in more than one table, or for more than one action (for example, both an add and an update action) in the same table. In this case, use a connection object, and pass it as an "obj" in your recordset calls. If you're reading from two different parts of the same table, you can read the first row(s) with one recordset and store that information (else it would be overwritten); then you can reuse the same recordset to read the second row(s).

The CML/LitCrit application Ddetails.asp page instantiates three different recordsets because it uses three RDS controls to hold item data (title, subject, and authors) for simultaneous data-binding and display. (Reusing one recordset would overwrite the first two sets of retrieved data.) These RDS controls are used in the application's ASP pages.

Now the CML/LitCrit application uses the RDS datashape provider, but this doesn't affect the number of RDS objects needed because the datashape provider is used not on the ASP pages of the application but in a custom COM component.