Page 130 - DCAP402_DCAO204_DATABASE MANAGEMENT SYSTEM_MANAGING DATABASE

Unit 7: Relational Database Design

Notes
Figure 7.8: Aggregation

name
ssn lot

Employees

Monitors until

since
started_on dname
pid pbudget did budget

Projects Sponsors Departments

Consider the Sponsors relation. It has attributes pid, did, and since, and in general we need it (in
addition to Monitors) for two reasons:
1. We have to record the descriptive attributes (in our example, since) of the Sponsors
relationship.
2. Not every sponsorship has a monitor, and thus some pid, did pairs in the Sponsors relation
may not appear in the Monitors relation.
However, if Sponsors has no descriptive attributes and has total participation in Monitors,
every possible instance of the Sponsors relation can be obtained by looking at the pid, didcolumns
of the Monitors relation. Thus, we need not store the Sponsors relation in this case.

Task How many foreign key available on single table?



Case Study Data Warehousing: A Strategic Tool

atawarehouse is a massive independent business database system that is populated
with data that has been extracted from a range of sources. The data is held
Dseparately from its origin and is used to help to improve the decision-making
process.
Many traditional Databases are involved in recording day to day operational activities of
the business, called online transaction processing (OLTP)., commonly implemented in
Airline Bookings & Banking Systems, for fasters response and better control over data.
Contd...

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