Hierarchical Recordsets

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Data doesn't exist in a vacuum. If you build an order entry system and the user requests data for a particular order, you'll probably include information from more than one table. Maybe you'll want to display the information from the Customers table about the customer who placed the order, as well as the items from the Orders table that make up the order.

The ADO Cursor Engine includes functionality that lets you organize data from separate tables into a hierarchy. You can issue a single query that retrieves information such as customer, order, and order detail into different levels of a hierarchy. As you navigate through the customer level of the hierarchy, you'll see only the orders that apply to that customer. And as you look at a particular order, you'll see only those items that the order includes.

In Chapter 14, you'll see how ADO organizes this data and synchronizes it in your hierarchy. The query syntax to build the hierarchy is somewhat confusing. We'll look at some examples of this syntax without going into too much depth. The topic of hierarchical query syntax could fill an entire book. The goal in Chapter 14 is to help you understand how this feature works so that you can use it intelligently and avoid coding yourself into a corner.