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Quiz 14 :

Relational Databases and Database Design.

Quiz 14 :

Relational Databases and Database Design.

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What are the formal names for a table, for a row, and for a column What are the popular names for a row and for a column
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a.
• A table is a set of rows and columns.
• Each table is identified by a unique name.
• Multidimensional representation of a table gives detailed information in a simple manner.
• It is possible to have many numbers of rows and columns in a table.
• Information in a table can be edited whenever needed.
• Table can be specified with orientation, order by.
• Table includes several text-formatting options.
Formal names for a table, row, column:
• A formal name for a table is a relation, file.
• A formal name for a row is tuple, periods, and vector.
• A formal name for a column is attribute, groups, and parameter.
An example student table with rows and columns is
img This table contains four rows and four columns giving information about students in the school.
b.
• Each rows of the table are independent and it is dependent on particular column.
• Table represents student details; each row in a table gives information about a particular student.
• Each record is a unit of information in the field. It contains combination of data types.
• Columns are independent and every column has a unique name. It is identified by its unique name.
• Every column has a separate data type and field value must belong to that data type.
• In the student table, student ID is a number data type, first name, last name belongs to text data type, and age field is a number data type.
• Number data type allows only numbers and text allows only letters.
Popular names for a row and column:
• Popular names for a row are record.
• Popular names for a column are field.

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What is a domain
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Domain
• A domain contains the values that are acceptable by the particular field in the database table.
• It describes the set of possible values for a given attribute.
• Attributes are nothing but fields in the database table. It protects the integrity of data in database.
• Domain simply refers to the description of attributes.
• Domain integrity allows only the valid set of all possible values for a field. It is enforced by restricting the invalid data type for attribute, whether the field can contain null value or can it be assigned default value or the value for a particular attribute is unique.
• Domain defines the specific conditions for particular attribute.
• Field in database table will not accept the value that is not available in that domain.
• Domain also provides constraints for the attribute. Constraints restrict the value entered to be within the range. In range domain, it limits the choice of the value for particular attribute.
• If the rule for the attribute is to contain the positive value, then negative values are not allowed.
• When the numeric value is limited to the length 6 digits for pin code attribute, it does not allow entering more than 6 digits.
Example: When the attribute is a date, domain prevents the user from entering the invalid date by giving conditions.
Example: In the student table, it contains the attributes first name and last name; only the text values are permitted in that field not an integer value.

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What is an entity
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Entity
• An entity is the schema for the table about which the data can be collected for processing information.
• Each table holds the collection of information about object, person such as student, teacher, and things such as books.
• An entity is a data element represented by a set of attributes in a table.
• Entities are independent. One entity is distinct from the other entity.
Example: Consider employee table having fields employee number, employee name, job, salary, and department. Here employee is the entity and employee number, employee name, job, salary, and department are attributes.
Entity set
Collection of entities of same type is called as entity set. Entity set are nothing but rows in the table.
Entity set are categorized into two types. They are
1. Strong entity set
2. Weak entity set
Strong entity set
• An entity set which has the sufficient number of attributes with its own unique identification is called strong entity set.
• An entity that has a primary key is called as strong entity.
• Example: Consider employee table having fields employee number, employee name, job, salary, and department. Here employee is the entity and employee number, employee name, job, salary, and department are attributes. Employee number is the primary key that uniquely identifies each row of table employee. Hence, employee is a strong entity.
Weak entity set
• An entity set which may not have the sufficient number of attributes with its own unique identification is called weak entity set.
• An entity that does not have a primary key of its own is called as weak entity.
• Example: Consider the account table with attributes such as customer account number, savings account, current account. Customer account number is sequential number generated for each customer in bank. Each account entity is distinct, but account type for each customer shares the same account number and so it does not have the primary key. It form the weak entity set.

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What is the relationship between a primary key and a candidate key
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What is a composite key
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What is a foreign key
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Look for an example of a one-to-one relationship, an example of a one-to-many relationship, and an example of a many-to-many relationship in a newspaper, magazine, book, or everyday situation you encounter.
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When do you use an entity subtype
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What is the entity integrity constraint
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What is referential integrity
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What does the cascades option, which is used with referential integrity, accomplish
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What are partial and transitive dependencies
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What three types of anomalies can be exhibited by a table, and what problems do they cause
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Figure A-24 shows the Employee, Position, and Employment tables with primary keys EmployeeNum, PositionID, and both EmployeeNum and PositionID, respectively. Which two integrity constraints do these tables violate and why Figure: Integrity constraint violations img
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The State and City tables, shown in Figure A-4, are described as follows: State (StateAbbrev, StateName, EnteredUnionOrder, StateBird, StatePopulation) City (StateAbbrev, CityName, CityPopulation) Foreign key: StateAbbrev to State table Figure: StateAbbrev as a primary key (State table) and a foreign key (City table) img Add the field named CountyName for the county or counties in a state containing the city to this database, justify where you placed it (that is, in an existing table or in a new one), and draw the entity-relationship diagram for all the entities. Counties for some of the cities shown in Figure A-4 are Travis and Williamson counties for Austin TX; Hartford county for Hartford CT; Clinton, Eaton, and Ingham counties for Lansing MI; Davidson county for Nashville TN; Hughes county for Pierre SD; and Nueces and San Patricio counties for Portland TX.
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Suppose you have a table for a dance studio. The fields are dancer's identification number, dancer's name, dancer's address, dancer's telephone number, class identification number, day that the class meets, time that the class meets, instructor name, and instructor identification number. Assume that each dancer takes one class, each class meets only once a week and has one instructor, and each instructor can teach more than one class. In what normal form is the table currently, given the following alternative description Dancer (DancerID, DancerName, DancerAddr, DancerPhone, ClassID, ClassDay, ClassTime, InstrName, InstrID) Convert this relation to 3NF and represent the design using the alternative description method.
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Store the following fields for a library database: AuthorCode, AuthorName, BookTitle, BorrowerAddress, BorrowerName, BorrowerCardNumber, CopiesOfBook, ISBN (International Standard Book Number), LoanDate, PublisherCode, PublisherName, and PublisherAddress. A one-to-many relationship exists between publishers and books. Many-to-many relationships exist between authors and books and between borrowers and books. a. Name the entities for the library database. b. Create the tables for the library database and describe them using the alternative method. Be sure the tables are in third normal form. c. Draw an entity-relationship diagram for the library database.
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In the database shown in Figure A-25, which consists of the Department and Employee tables, add one record to the end of the Employee table that violates both the entity integrity constraint and the referential integrity constraint. Figure: Creating integrity constraint violations img
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Consider the following table: Patient (PatientID, PatientName, BalanceOwed, DoctorID, DoctorName, ServiceCode, Service- Desc, ServiceFee, ServiceDate) This is a table concerning data about patients of doctors at a clinic and the services the doctors perform for their patients. The following dependencies exist in the Patient table: PatientID PatientName, BalanceOwed DoctorID DoctorName ServiceCode ServiceDesc, ServiceFee PatientID, DoctorID, ServiceCode PatientName, BalanceOwed, DoctorName, ServiceDesc, ServiceFee, ServiceDate a. Based on the dependencies, convert the Patient table to first normal form. b. Next, convert the Patient table to third normal form.
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Suppose you need to track data for mountain climbing expeditions. Each member of an expedition is called a climber, and one of the climbers is named to lead an expedition. Climbers can be members of many expeditions over time. The climbers in each expedition attempt to ascend one or more peaks by scaling one of the many faces of the peaks. The data you need to track includes the name of the expedition, the leader of the expedition, and comments about the expedition; the first name, last name, nationality, birth date, death date, and comments about each climber; the name, location, height, and comments about each peak; the name and comments about each face of a peak; comments about each climber for each expedition; and the highest height reached and the date for each ascent attempt by a climber on a face with commentary. a. Create the tables for the expedition database and describe them using the alternative method. Be sure the tables are in third normal form. b. Draw an entity-relationship diagram for the expedition database.
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