12 Hierarchies
If you think education is expensive, try ignorance.—Derek Bok, former president of Harvard.
A hierarchy is special kind of data structure made up of nodes connected to one another via oneway relationships known as edges. These nodes exist at multiple levels and roughly resemble a tree—in fact, you’ll often hear the terms “hierarchy” and “tree” used interchangeably. Out of the box, Transact-SQL provides only meager support for hierarchies and trees. Other products such as Oracle have decent tree support, but Transact-SQL is strangely lacking here. This isn’t the limitation that it might seem, though, because there are a number of straightforward techniques that make displaying and manipulating hierarchies fairly simple in ...
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