IT-510-X2473: Assignment 7-2
SNHU
1. What is a DBMS? Briefly describe the components of DBMS.
DBMS is short for Database Management System. aa It is a set of different software that
help to organize, store and retrieve data.
Components:
1. Users,
2. Database administrators
3. Related information systems.
4. Data manipulation language
5. Schema
6. Physical data repository
2. aa Describe a primary key, candidate key, secondary key, foreign key, and a
combination key. Use your imagination to provide an example of each key that is
not in the textbook.
Primary key: One or more columns that uniquely identify each row in the table (only
one per table allowed. No nulls allowed). e.g Passport number, insurance ID etc.
Candidate key: Any key that can be used as a primary key e.Drivers license number
instead of SSN.
Secondary key: A field or combination of fields to retrieve data e.g requirement of first
name and last name along with passport number to get I-90 form information.
Foreign key: One or more columns in a table that refer to a primary key in another
table.
Combination key: When two different fields combine to generate a result, the fields
altogether are called combination keys.
3. What are entity-relationship diagrams and how are they used? What symbol is
used for a relationship? What is an associative entity? Provide an example
According to the definition in our text, ERD is a model that shows the logical
relationships and interaction among system entities (Shelly 360). Relationships are the
link that is represented by a diamond shape which is labeled with verbs. Moreover, an
associative entity is a third entity (or base relation) that links the two other entities.
For Example: Realtor aa is the associative entity
Sale
References
Shelly, Gary B., and Harry J. Rosenblatt. Systems Analysis and Design. 10th ed.
Boston: Course Technology Cengage Learning, 2016. Print.
Real Estate Company
(CM Builders:
Broker)
Home Buyers
Realtor
(CM Builders: Employee)
