Databases Reference
In-Depth Information
Figure 3-9
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B-Tree
Index
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Data File
B-tree index.
FOR EXAMPLE
Entities, Attributes, and Objects
Suppose that you are creating a database for a private golf course. It includes
full members who have access to all facilities and limited members who are
allowed on the course and in the Pro Shop only. The Pro Shop keeps a small
inventory of items available for purchase and also keeps track of tee time
reservations and golf carts.
There are several entities that should come to mind immediately, such
as members, employees, inventory, and golf carts. These are all tangible enti-
ties. What about intangible entities? One already mentioned is tee times, and
others will probably come to mind as you think about activities around a
golf course and private clubhouse.
However, some decisions might not be as obvious as they would seem at
first glance. For example, how many tables will you need to track the member
entity? Should full and limited members be tracked in the same table or do you
need separate tables? This points out the need for gathering as much informa-
tion as possible before you make modeling decisions. Right now, you probably
don't know enough about the data requirements to make that decision, so you
need to go back to your human data sources and ask more questions.
