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Database Systems: Design, Implementation, and Management: Chapter 1
1. 1. Define each of the following terms:
a. data
b. field
c. record
d. file: Data: raw facts
Field: an attribute, same data type Record: related data that describes an entity File: a collection of related records.
2. 2. What is data redundancy, and which characteristics of the file system can lead to it?: Data redundancy occurs when the
same data are stored in multiple places unnecessarily. The use of spreadsheets and tables in ditterent parts of the organization can cause it.
3. 3. What is data independence, and why is it lacking in file systems?: Data independence exists when you can change the data storage
characteristics without impeding the program's ability to access the data.
4. 4. What is a DBMS, and what are its functions?: DBMS = Database Management System
a collection of programs that manages the database structure and controls access to the data stored in the database. (think electronic filing cabinet) functions of a DBMS:
2 / data dictionary management data storage management data transformation and presentation security management multi user access control backup and recovery management data integrity management database access languages and application programming interfaces. database communication interfaces.
5. 5. What is structural independence, and why is it important?: When it is possible to make changes in the file structure without
affecting the application program's ability to access the data.
6. 6. Explain the differences among data, information, and a database.: Data are raw facts that have not been processed. Information is
data that has been processed and given context. Databases help to facilitate the manipulation of data to create information by providing an organizational structure that makes relationships and connections between data explicit.
7. 7. What is the role of a DBMS, and what are its advantages? What are its disadvantages?: serves as the intermediary
between the user and the database. advantages: improved data sharing improved data security better data integration minimized data inconsistency improved data access improved decision making
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- operational/transactional/production database: for day-to-day operations
- data warehouse: stores data used to generate info required to make tactical or strategic decisions
9. 9. What are the main components of a database system?: hardware software
people procedures data
10. 10. What are metadata?: data about data, through which the end user data are integrated and managed.
11. 11. Explain why database design is important.: a poorly designed database may produce diflcult to trace errors that result in bad
decision making -- and bad decision making can lead to the failure of an organization.
12. 12. What are the potential costs of implementing a database system?: - sophisticated hardware and software,
trained personnel
- training, licensing and regulation compliance costs
- vendor dependence - vendors are less likely to otter pricing point advantages to existing customers
- updating of hardware and software; additional training
13. 13. Use examples to compare and contrast unstructured and structured data. Which type is more
prevalent in a typical business environment?: unstructured data is simply data that has not been processed to yield information. examples of both types would include:
5 / An invoice. If one were to take an invoice and simply scan it into a graphic, it would be unstructured data. In contrast, if it were processed and put into a database (subsequently becoming structured data), employees could eventually find the monthly averages, amount owed, etc. from various invoices. While both are prevalent, I would think semi-structured data would be the most common in a typical business. Some data is stored but not processed (unstructured data such as memos), and some others are stored in databases (such as invoices) but most data are only processed to a certain extent that is displayed in a prearranged format but not able to yield all of the information contained within.
14. 14. What are some basic database functions that a spreadsheet cannot perform?: spreadsheets do not
support basic functionality such as: support for self-documentation through metadata enforcement of data types or domains to ensure consistency of data within a column, defined relationships among tables, or contraints to ensure consistency of data across related tables.
15. 15. What common problems does a collection of spreadsheets created by end users share with the typical file
system?: Common problems with using both a collection of spreadsheets created by end users and the typical file system include: lengthy development times difficulty of getting quick answers complex system administration lack of security and limited data sharing extensive programming
16. 16. Explain the significance of the loss of direct, hands-on access to business data that end users
experienced with the advent of computerized data repositories: The loss of direct, hands on access to business data to end-users was significant because it gave them the tools to convert their data into the information they needed and manipulating the company data that would allow them to create new information.
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23. Why is an object said to have greater semantic content than an entity?: An object has greater semantic content because it
embodies both data and behavior. That is, the object contains, in addition to data, also the description of the operations that may be performed by the object.
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24. What is the difference between an object and a class in the object oriented data model?: An object is an instance of
a specific class. It is useful to point out that the object is a run-time concept, while the class is a more static description. Objects that share similar characteristics are grouped in classes. A class is a collection of similar objects with shared structure (attributes) and behavior (methods.) Therefore, a class resembles an entity set. However, a class also includes a set of procedures known as methods.
25. What is an ERDM and what role does it play in the modern (production) database environment?:
26. What is a relationship, and what three types of relationships exist?: A relationship is an association among (two or more)
entities. Three types of relationships exist: one-to-one (1:1), one-to-many (1:M), and many-to-many (M:N or M:M.)
27. What is a table and what role does it play in the relational model?: Relational data model bases data storage on relations.
These relations are based on algebraic set theory. However, the user perceives the relations to be tables. In the relational database environment, designers and users perceive a table to be a matrix consisting of a series of row/column intersections.Tables, also called relations, are related to each other by sharing a common entity characteristic. For example, an INVOICE table would contain a customer number that points to that same number in the CUSTOMER table. This feature enables the RDBMS to link invoices to the customers who generated them. Tables are especially useful from the modeling and implementation perspectives. Because tables are used to describe the entities they represent, they provide an easy way to summarize entity characteristics and relationships among entities. And, because they are purely conceptual constructs, the designer does not need to be concerned about the physical implementation aspects of the database design.
28. What is a relational diagram? Give an example: A relational diagram is a visual represen- tation of the relational database's entities,
the attributes within those entities, and the relationships between those entities. Therefore, it is easy to see what the entities represent and to see what types of relationships (1:1, 1:M, M:N) exist among the entities and how those relationships are implemented.
29. What is connectivity?: The ER model uses the term connectivity to label the relationship types. The name of the relationship is usually an active or
passive verb
30. Describe the Big Data phenomenon.: A movement to find new and better ways to manage large amounts of Web-generated data and derive
business insight from it, while simultaneously providing high performance and scalability at a reasonable cost.
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38. Why are entity integrity and referential integrity important in a database?: -
Entity integrity is important because it means that a proper search for an existing tuple will always be successful and the failure to find a match on a row search will always mean that the row for which the search is conducted does not exist in that table. Referential integrity is important because its existence ensure that it will be impossible to assign a non existing foreign key value to a table. For example, the referential integrity enforcement in a SALESREP is assigned to CUSTOMER relationship means that it will be possible for a customer to not have a sales rep assigned to him or her but it will be impossible to assign non existing sales rep to a customer.
39. What are the requirements that two relations must satisfy to be considered union-compatible?: Using the proper
relational terminology, the statement may be translated to " the table or entity set contains two hundred rows/tuples.
40. Which relational algebra operators can be applied to a pair of tables that are not union compatible?: Select,
Project, Divide, Product, and Join
41. Explain why the data dictionary is sometimes called "the database designer's database": Because it contains metadata
relating to the datatypes used and sizes as well has the relations in the database.
42. A database user manually notes that "The file contains two hundred records, each record containing
nine fields." Use appropriate relational database termi- nology to "translate" that statement.: An entity set contains two hundred tuples with each record consisting of nine attributes.
43. What two conditions must be met before an entity can be classified as a weak entity?: - Existence-dependent - Has a
primary key partially or totally derived from the parent entity in the relationship
44. What is a strong (or identifying) relationship, and how is it depicted in a Crow's Foot ERD?: A strong relationship
is when an entity is existence-dependent on another entity and inherits at least part of its primary key from that entity
45. What is a composite entity, and when is it used?: A composite entity is generally used to transform M:N relationships into 1:M
relationships. A composite entity, also known as a bridge entity, is one that has a primary key composed of multiple attributes. The PK attributes are inherited from the entities that it relates to one another.
