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Questions and Answers of Databases

A pet store currently uses a legacy flat file system to store all of its information. The owner of the store, Peter Corona, wants to implement a Web-enabled database application. This would enable
For Problem and Exercise 4-50, draw the ER diagram based on the normalized relations.
How would Problems and Exercises 4-50 and 4-51 change if a type of fish could be supplied by multiple suppliers?Exercises 4-50
Figure 4-40 shows an EER diagram for a university dining service organization that provides dining services to a major university. a. Transform the EER diagram to a set of relations and develop a
Explore the data included in Table 4-9.Assume that the primary key of this relation consists of two components: Author's ID (AID) and Book number (BNbr). The relation includes data regarding authors,
The following attributes form a relation that includes information about individual computers, their vendors, software packages running on the computers, computer users, and user authorizations.
The following attributes represent data about a movie copy at an online video rental service. Each movie is identified by a movie number and has a title and information about the director and the
A start-up is working on an online personal financial management system. The goal of the system is to provide the users an opportunity to obtain item-level purchase data from as many sources as
A bus company is responsible for offering public transportation in the suburbs of a large metropolitan area. The company has significant data management requirements: It needs to keep track of its
Interview system designers and database designers at several organizations. Ask them to describe the process they use for logical design. How do they transform their conceptual data models (e.g., E-R
Describe two properties that each candidate key must satisfy.
Map the EER diagram you developed in Chapter 3, 3-44 to a relational schema using the techniques described in this chapter. Be sure to appropriately identify the primary and foreign keys as well as
If necessary, revisit and modify the EER diagram you created in Chapter 3, 3-44 to reflect any changes made in answering 4-64 and 4-65 above.
Describe three types of anomalies that can arise in a table and the negative consequences of each.
Demonstrate each of the anomaly types with an example.
Define each of the following terms:a. File organizationb. Heap file organizationc. Sequential file organizationd. Indexed file organizatione. Hashed file organizationf. Denormalizationg. Composite
Why are field values sometimes coded?
Describe three ways to handle missing field values.
Explain why normalized relations may not comprise an efficient physical implementation structure.
Explain why it makes sense to first go through the normalization process and then denormalize.
List three common situations that suggest that relations be denormalized before database implementation.
Explain the reasons why some experts are against the practice of denormalization.
What are the advantages and disadvantages of horizontal and vertical partitioning?
List seven important criteria for selecting the best file organization.
What are the benefits of a hash index table?
Match the following to the appropriate definitions: _________ Extent a. a detailed coding scheme for representing organizational data _________ Hashing algorithm b. a data structure used to
What is the purpose of clustering of data in a file?
What is the most important mechanism that database designers can use to impact database performance in specific use situations?
State nine rules of thumb for choosing indexes.
One of the recommendations regarding indexes is to specify a unique index for each primary key. Explain the justification for this recommendation.
Explain why an index is useful only if there is sufficient variety in the values of an attribute.
Indexing can clearly be very beneficial. Why should you not create an index for every column of every table of your database?
Explain the reasons underlying the significant performance gains in query performance that can be achieved with parallel processing.
Consider the following two relations for Millennium College: Following is a typical query against these relations: a. On what attributes should indexes be defined to speed up this query? Give the
Choose Oracle data types for the attributes in the normalized relations in Figure 5-4b. DBMS you are using is Oracle. If that is not the case, feel free to modify the question for the DBMS
Choose Oracle data types for the attributes in the normalized relations that you created in Problem and Exercise 4-47 in Chapter 4.DBMS you are using is Oracle. If that is not the case, feel free to
Contrast the following terms:a. Horizontal partitioning; vertical partitioningb. Physical file; tablespacec. Normalization; denormalizationd. Range control; null controle. Secondary key; primary key
Explain in your own words what the precision (p) and scale (s) parameters for the Oracle data type NUMBER mean. DBMS you are using is Oracle. If that is not the case, feel free to modify the question
Say that you are interested in storing the numeric value 3,456,349.2334. What will be stored, with each of the following Oracle data types: a. NUMBER (ll) b. NUMBER (11,1) c. NUMBER (ll,-2) d. NUMBER
Suppose you are designing a default value for the age field in a student record at your university. What possible values would you consider, and why? How might the default vary by other
When a student has not chosen a major at a university, the university often enters a value of "Undecided" for the major field. Is "Undecided" a way to represent the null value? Should it be used as a
Consider the following normalized relations from a database in a large retail chain: What opportunities might exist for denormalizing these relations when defining the physical records for this
Consider the following set of normalized relations from a database used by a mobile service provide to keep track of its users and advertiser customers. Assume that the mobile service provider has
Consider the following normalized relations for a sports league: What recommendations would you make regarding opportunities for denormalization? What additional in-formation would you need to make
What problems might arise from vertically partitioning a relation? Given these potential problems, what general conditions influence when to partition a relation vertically?
Is it possible with a sequential file organization to permit sequential scanning of the data, based on several sorted orders? If not, why not? If it is possible, how?
What are the major inputs into physical database design?
Suppose each record in a file were connected to the prior record and the next record in key sequence using pointers. Thus, each record might have the following format: Primary key, other attributes,
Assume that a student table in a university database had an index on StudentID (the primary key) and indexes on Major, Age, MaritalStatus, and HomeZipCode (all secondary keys). Further, assume that
Consider the relations specified in Problem and Exercise 5-37. Assume that the database has been implemented without denormalization. Further assume that the database is global in scope and covers
Consider Figure 5-7b. Assuming that the empty rows in the leaves of this index show space where new records can be stored, explain where the record for Sooners would be stored. Where would the record
Consider Figure 4-38 and your answer to Problem and Exercise 4-48 in Chapter 4. Assume that the most important reports that the organization needs are as follows: • A list of the current
Can clustering of files occur after the files are populated with records? Why or why not?
Parallel query processing, as described in this chapter, means that the same query is run on multiple processors and that each processor accesses in parallel a different subset of the database.
Consider the EER diagram in Figure 4-33. Let's make the following assumptions:• There are 12,500,000 customers.• These customers have altogether 40,000,000 card accounts. Of these 80 percent are
Create a join index on the CustomerlD fields of the Customer_T and Order_T tables in Figure 4-4. Pine Valley Furniture Company data set provided with the text.
Consider the composite usage map in Figure 5-1. After a period of time, the assumptions for this usage map have changed, as follows: • There is an average of 50 supplies (rather than 40) for each
What are the key decisions in physical database design?
Consider the EER diagram for Pine Valley Furniture shown in Figure 3-12. Figure 5-9 looks at a portion of that EER diagram. Let's make a few assumptions about the average usage of the system: •
Refer to Figure 4-5. For each of the following reports (with sample data), indicate any indexes that you feel would help the report run faster as well as the type of index:a. State, by products
Find out which database management systems are available at your university for student use. Investigate which data types these DBMSs support. Compare these DBMSs based on the data types supported
Using the Web site for this text and other Internet resources, investigate the parallel processing capabilities of several leading DBMSs. How do their capabilities differ?
Contact a database designer or administrator in an organization with which you are familiar. Ask what file organizations are available in the various DBMSs used in that organization. Interview this
Do you see any justifiable opportunities to denormalize the tables? If so, provide appropriate justification and create a new denormalized schema. Do you need to update your ER diagram based on these
Create a data dictionary similar to the metadata table shown in Table 1-1 in Chapter 1 to document your choices. For each table in the relational schema you developed earlier, provide the following
Create the physical data model for the relational schema you developed in Chapter 4 (and potentially modified in 5-56 above), clearly indicating data types, primary keys, and foreign keys.
Create a strategy for reviewing your deliverables generated so far with the appropriate stakeholders. Which stakeholders should you meet with? What information would you bring to this meeting? Would
What decisions have to be made to develop a field specification?
Explain how physical database design has an important role in forming a foundation for regulatory compliance.
Explain why you sometimes have to reserve much more space for a numeric field than any of the initial stored values require.
Define each of the following terms:a. Base tableb. Data definition languagec. Data manipulation languaged. Dynamic viewe. Materialized viewf. Referential integrity constraintg. Relational DBMS
Explain how referential integrity is established in databases that are SQL:1999 compliant. Explain how the on update restrict, on update cascade, and on update set null clauses differ from one
Explain some possible purposes of creating a view using SQL. In particular, explain how a view can be used to reinforce data security.
Explain why it is necessary to limit the kinds of updates performed on data when referencing data through a view.
Describe a set of circumstances for which using a view can save reprogramming effort.
Drawing on material covered in prior chapters, explain the factors to be considered in deciding whether to create a key index for a table in SQL.
Explain and provide at least one example of how to qualify the ownership of a table in SQL. What has to occur for one user to be allowed to use a table in a database owned by another user?
How is the order in which attributes appear in a result table changed? How are the column heading labels in a result table changed?
What is the difference between COUNT, COUNT DISTINCT, and COUNT(*) in SQL? When will these three commands generate the same and different results?
What is the evaluation order for the Boolean operators (AND, OR, NOT) in an SQL command? How can a query writer be sure that the operators will work in a specific, desired order?
Match the following terms to the appropriate definitions: _________ View a. list of values _________ Referential b. description of a database _________ Integrity constraint c. view materialized as
Describe a situation in which you would need to write a query using the HAVING clause.
In what clause of a SELECT statement is an IN operator used? What follows the IN operator? What other SQL operator can sometimes be used to perform the same operation as the IN operator? Under what
Explain why SQL is called a set-oriented language.
What is an identity column? Explain the benefits of using the identity column capability in SQL.
SQU2006 and SQL:2008 introduced a new keyword, MERGE. Explain how using this keyword allows one to accomplish updating and merging data into a table using one command rather than two.
In what order are the clauses of an SQL statement processed?
In an ORDER BY clause, what are the two ways to refer to the columns to be used for sorting the results of the query?
Contrast the following terms:a. Base table; viewb. Dynamic view; materialized viewc. Catalog; schema
Explain the purpose of the CHECK clause within a CREATE TABLE SQL command. Explain the purpose of the WITH CHECK OPTION in a CREATE VIEW SQL command.
What can be changed about a table definition, using the SQL command ALTER? Can you identify anything about a table definition that cannot be changed using the ALTER command?
Explain the difference between the WHERE and HAVING clause.
Is it possible to use both a WHERE clause and a HAVING clause in the same SQL SELECT statement? If so, what are the different purposes of these two clauses?
Write a database description for each of the relations shown, using SQL DDL (shorten, abbreviate, or change any data names, as needed for your SQL version). Assume the following attribute data types:
Write SQL data definition commands for each of the following queries: a. How would you add an attribute, Class, to the Student table? b. How would you remove the Registration table? c. How would you
Write SQL commands for the following: a. Create two different forms of the INSERT command to add a student with a student ID of 65798 and last name Lopez to the Student table. b. Now write a command
What are SQL-92, SQL:1999, and SQL:2011? Briefly describe how SQL:2011 differs from SQD1999.
Write SQL queries to answer the following questions: a. Which students have an ID number that is less than 50000? b. What is the name of the faculty member whose ID is 4756? c. What is the smallest
Write SQL queries to answer the following questions: a. How many students are enrolled in Section 2714 in the first semester of 2015? b. Which faculty members have qualified to teach a course since
Write SQL queries to answer the following questions:a. Which students are enrolled in Database and Networking?b. Which instructors cannot teach both Syst Analysis and Syst Design?c. Which courses

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