Databases Reference
In-Depth Information
Exhibit 26-1. A data model for ron's real estate business.
This similarity enables at least the initial steps of relational design to be a
straight-forward process.
An intuitive first attempt at a relational database design to support Ron's
Real Estate Business (depicted in Exhibit 1) would probably include five
tables, one for each entity in the data model: RENTER, PROPERTY, RENTAL-
AGREEMENT, BEACH-PROPERTY, and MOUNTAIN-PROPERTY. The RENTER
table would then have four columns representing NAME, ADDRESS,
PHONE-NUMBER, and MAX-MONTHLY-RENT-AMT. The values of these col-
umns should comply with the integrity rules identified in the logical data
model. Some implementation mechanisms for enforcing those integrity
rules include using a DBMS to specify NOT NULL and create a unique index
on entity identifier columns, and enforcing other domain rules (such as
data type or even default value) through the data definition language.
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