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Database Management Systems/Managing Database

Notes 3. Use an Entity-Relationship diagram to depict the information needs of a small computer
business firm:
(a) The employees of the company assemble different types of computers. For each
employee a record is kept of his employee no., name, address, phone no., job title,
and salary.

(b) A record is also kept of each of the machines model, specs and name, and quantity on
hand.
(c) Each machine consists of a number of parts. An inventory must be kept of the parts
in stock. For each part a record is kept of its name, price, and quantity on hand.
(d) These parts are ordered from various suppliers. A record must be kept of the
suppliers name, address, and phone number.
(e) The assembled computers are sold to various customers. A record is kept of the
customers name, address, and phone number. Some of these customers are credit
customers and for these customers a record is kept of their credit limit.
4. Why are entity integrity and referential integrity important in a database?
5. Suppose that you are using the database composed of the two tables shown in table below:

(a) Identify the primary keys.
(b) Identify the foreign keys.

(c) Draw the entity relationship model.

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