Module 1 Flashcards
A business keeps track of their employees, shifts and dates worked using only the following file:
After learning that Elizabeth Linbreck ceased employment with the business, her entity was deleted from the file, which now looks like this:
Due to the structure of the file, which of the following will occur as a result of this deletion?
A. An update anomaly
B. An insertion anomaly
C. A deletion anomaly
D. An error message will display
ANSWER: C
This file is the only source of both the employee names and the possible shifts. Elizabeth Linbreck was the only one working on the “First-Second Shift”. Therefore, deleting Elizabeth Linbreck from the file also deleted any information regarding “First-Second Shift”. This is known as a deletion anomaly
Read the scenario below, then follow the subsequent instructions.
A small organization stores its data in a file named “ORGDATA.xyz”, and uses a custom program to store and access the data in the file. The file is in a format that was created by the organization. Two years ago, the technical team decided to upgrade the file format by moving all records for the same clients physically close to each other in the file. This upgrade necessitated a change to the custom program in order for it to know how to access the data. Last year, the technical team decided to upgrade the file by allowing 255 characters for each client last name, instead of the original 16 characters. This upgrade again required a change to the custom program. Lastly, the file format has no way for one record to reference another record. For example, if two clients live at the same address, the address must be included twice in the file – once for each client.
Select all statements that correctly describe the above scenario.
A. The customer program used to store and access data in the file is structurally dependent upon the file.
B. The file is subject to data anomalies
C. It is impossible to answer any ad-hoc (spur of the moment) questions using the file and program.
D. The customer program used to store and access the data in the file is data dependent upon the file.
E. The file exhibits data redundancy
Answer: A, B, D, E
The file exhibits data redundancy because records cannot reference other records, and so two logically equal pieces of data must sometimes be duplicated. We know this from the fact that the same address is listed once for each client. The customer program used to store and access data in the file is structurally dependent upon the file. because the scenario indicates that two years ago, a change to the structure required a change to the program. The file is subject to data anomalies because it exhibits data redundancy. Any system that allows for duplicate data is subject to update, insertion, and deletion anomalies. The program is data dependent because the scenario indicates that last year, the datatype of one of the fields changed, and that the program needed to change to continue accessing the file. Though use of a DBMS make ad-hoc questions easier to answer, existing data in a file can still be used to do the same.
Select all statements that correctly describe an attribute in the relational model.
A. An attribute is a data characteristic of an entity, such as the datae of an order.
B. The existence and properties of an attribute of an entity might be discovered from the business rules.
C. An attribute is the rough equivalent of a field in a file system.
D. Data is more secure when stored in a basic file system than when it is stored in a DBMS.
E.An example of an attribute may be a customer last name
Answer: A, B, C, E
Attributes are used to describe an entity. The field in a file system is an attribute. A row is an entity. An attribute is a characteristic of an entity. A customer last name could be a field in the customer table. Data is more secure when it is stored in a DBMS, since a DBMS has many fine-tuned privileges and other advanced security mechanisms.
- Read the following paragraph, then follow the subsequent instructions:
At times, photographers employed at this agency may take many publishable photographs in a single day, although taking many publishable photographs may not be possible due to extreme weather or other unforeseen circumstances.
Most photographers employed at this agency are very capable individuals.
Select all statements that correctly assert a reason why the paragraph is not suitable to be a business rule.
A. Because the paragraph is not precise, it is not suitable to be a business rule.
B. Because the paragraph is ambiguous, it is not suitable to be a business rule.
C. Because the paragraph does not state the intended message concisely, it is not suitable to be a business rule.
D. Because the paragraph is not entertaining and exciting, it is not suitable to be a business rule.
E. Because the paragraph does not define entities clearly, it is not suitable to be a business rule.
ANSWER: A, B,C
Business rules must be correct, brief, precise, and unambiguous; having entertainment value is not considered important for a business rule. Business rules must be brief so that its intended meaning can be converted easily into database and system requirements. The above paragraph does not give precise inference to several ideas introduced, including how “very capable” would be modeled, nor the exact amount of “many publishable pictures”. The above paragraph mentions “many publishable pictures”, but does not provide any contrasting information to indicate how many or how much more than usual. There are several entities defined, including Photographer, Agency, and Photograph.
Select all statements that correctly describe business rules.
A. Business rules can be derived from an organization’s operations.
B. When designing databases, business rules are useful to businesses and government, but not to other types of organizations such as religious groups or research laboratories.
C. Business rules rarely describe details; they almost always describe high level items.
D. Business rules should be documented if they are to be used as a basis for a database design.
Answer: A, D
Business rules are helpful to all types of organizations. Business rules should be documented and reviewed. Business rules are commonly derived from the organizations operations. Business rules oftentimes describe details.
Select all statements that correctly describe business rules.
A. Some business rules help standardize an organization’s view of data.
B. Some business rules allow the designer to understand the nature, role, and scope of the data.
C. Some business rules act as a communications tool between users and designers.
D. Business rules define all applicable database constraints, no matter how detailed the constraint is.
E. Business rules are by definition valid for all data for all time, so they are well suited for database design.
Answer: A, B, C
Business rules must be easy to understand and widely disseminated, to ensure that every person in the organization shares a common interpretation of the rules. Some business rules are essential to database design because they allow the designer to know the scope of the data to be stored in the database. Business rules describe constraints on the data at a higher level, but particular implementations of constraints in the database are not explicitly defined by the business rules. Business rules help the users describe what is needed, and help designers understand what needs to be done. Business rules help everyone understand the company’s view.
You are given the following business rules:
- An actor acts in many movies.
- Each movie is acted in by many actors.
Select all alternatives below that correctly describe the relationship described by the business rules above.
A. This relationship can be represented by this entity relationship diagram:
B. This relationship can be classified as a one-to-many (1:M) relationship
C. This relationship can be represented by this entity relationship diagram:
D. This relationship can be classified as a many-to-many (M:N) relationship
Answer: A, D
Select all that is true of the conceptual model. (Check all that are true.)
A. Changes in the hardware or software will have no impact on the database design at the conceptual model level.
B. The conceptual model integrates all external views into a single global view of the data in the enterprise.
C. The most widely used conceptual model is the entity relationship model.
D. The conceptual model is independent of software, but dependent on hardware.
Answers: A, B,C
Select all that are true of constraints. (Check all that apply.)
A. A constraint can be a restriction that data must satisfy.
B. An example of a constraint when it is applicable to databases could be: A state code must be two characters.
C. A business rule is always a constraint.
D. The business rule, “We try to increase our prices when our main competitor increases their prices” would be appropriate to implement as a database constraint.
E. A constraint is important to help ensure data integrity.
Answers: A, B, E
Select all statements that are advantages of use a database management system (DBMS) over use of a basic file system.
A. Database systems can be designed to minimize the risks of data inconsistencies.
B. It is easier to change to a database system made by a different vendor than to change to a hard drive made by a different vendor.
C. Databases are easier to design and manage than spreadsheets.
D. Database systems improve the access to data, so there are fewer data anomalies and less redundancy.
Answer: A, D
Database systems improve the access to data, and can be designed to minimize the risks of data inconsistencies. Databases require skilled personnel to run them. Costs are high, and there is typically more data in a database to manage than a spreadsheet. It is more difficult to change database vendors than durable storage vendors. One reason is that both file systems and hard drive interfaces are highly standardized and are designed to be interoperable, while each DBMS has its own set of supported SQL, metadata, and tools.
Select all that is true of DBMS functions. (Check all that apply.)
A. Security management, backup and recovery management, and multiuser access control are important functions of commercial DBMS.
B. Common commercial DBMS provide data access through a query language.
C. One of the DBMS functions is control concurrent transactions.
D. Users are aware of all DBMS functions.
Answer: A, B, C
Select all statements that are disadvantages of using a database management system (DBMS) over use of a basic file system.
A. Database systems require complex DBMS software and skilled personnel, so costs can be higher than for spreadsheets or flat files.
B. DBMS vendors often upgrade their products, so there are additional costs to keep the database softwareup to date.
C. When only a small amount of data is stored, using a database for the data results in very poor performance when compared to using a file system for the data.
D. Typically more skilled personnel are needed to maintain database systems than to maintain basic file system storage.
A, B, D
Costs are higher with database systems due to the complexities and high salaries of the database staff. Vendors always update their products. This is nothing new, as with a tech product there are always new releases. DBMS are more complex than basic file systems, and thus necessitate more skilled personnel. For example, a DBMS may need its own dedicated database administrator, a database developer, and a data modeler. Databases are quite capable of handling small amounts of data, and still provide bettersecurity, performance, and ease of access when compared to file systems.
Select all statements that correctly describe a database management system (DBMS) function.
A. The DBMS makes it possible to query and update data.
B. Since the DBMS will allow more users to make updates, there will be more data inconsistencies.
C. The DBMS helps create an environment in which end users have better access to more and bettermanaged data.
D. The DBMS allows concurrent access to data.
E. The DBMS will make the data more available to users, so there will be more security breaches.
Answer: A, C ,D
Select all statements that correctly describe a database.
A. It is generally accepted that there are only three kinds of databases.
B. A database organizes data in a logical way.
C. A database management system helps manage the database and its data.
D. A database stores data about data to assist in data management.
Answer: B, C, D
Databases do indeed store metadata – data about data – to assist in the database’s management of the data. For example, when a table is created in a relational database, the database must store the names, number, and datatypes of the table’s columns. Unless data is stored in a logical way, it is not particularly useful. The database management system assists in managing the database itself, and helps controls access to the database. If the database is the library, the database management system is the librarian. There are many kinds of databases, which depend upon the number users supported, the kinds of use, and location. The database management system is generally the only mechanism through which the database’s data may be updated.
Select all statements that correctly describe a difference between a DBMS and a basic file system.
A. A properly designed file system exhibits structural independence, while a properly designed DBMS exhibits structural dependence.
B. A DBMS provides several important functions that guarantee the integrity and consistency of the data in the database, while file systems generally do not.
C. Extensive programming must be performed to retrieve, manipulate and store data in a DBMS, while a filesystem usually provides a language whereby data can be accessed, modified, and stored fairly easily.
D. Structural changes are difficult in a file system, and less difficult in a DBMS.
Answer: B, D
A properly designed file system exhibits structural dependence, while a properly designed DBMS exhibits structural independence. A DBMS has several functions to guarantee the integrity and consistency of the data in a database, including associating data types with data, providing nullability constraints, and providing security constraints. The DBMS usually provides a simpler query language, while extensive programming must be performed to do the same on a file system. Structural changes to a file require rewriting applications code; this is not often required with DBMS.
Select all statements that correctly describe a difference between a spreadsheet, such as Microsoft Excel, and a database, such as Oracle.
A. Spreadsheets typically hold more data than databases.
B. A spreadsheet can enforce some data type constraints, but doesn’t easily support discreet integrity constraintslike foreign keys.
C. A spreadsheet doesn t have native capabilities to manipulate data using a standard.
D. A spreadsheet does not support database functionalities like transactions, concurrency control or data integrity.
E. A database allows users to manipulate the data using a standard query language, but a spreadsheet does not.
Answers: B, C, D, E
A spreadsheet does not support many database functions such as concurrency, integrity enforcement, and transactions. Spreadsheets can enforce some constraints, but they are weak and do not do nearly as much as database constraints. A spreadsheet can have relationships, but they are harder to create and manage than a database. Spreadsheets do not have native capabilities to manipulate data using a standard like databases. Databases are usually much larger than spreadsheets. There are limitations in spreadsheets of how much data they can hold.
