Data Management Midterm

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A composite key consists of only one attribute. T/F

False

A constraint is a rule in a database system that can be violated by users. T/F

False

A foreign key is a primary key of a relation that also is a primary key in another relation. T/F

False

A member of a subtype does NOT necessarily have to be a member of the supertype. T/F

False

A relation is in first normal form if it has no more than one multivalued attribute. T/F

False

A subtype is a generic entity that has a relationship with one or more entities at a lower level. T/F

False

A transversal dependency is a functional dependency between two or more nonkey attributes. T/F

False

A user view is how the user sees the data when it is produced. T/F

False

A well-structured database establishes the entities between relationships in order to derive the desire information. T/F

False

CASE tools can model more complex data relationships, such as ternary relationships. T/F

False

Creating a data model from a packaged data model requires much more skill than creating one from scratch. T/F

False

Data intergrity consists of powerful operations to manipulate data stored in relations. T/F

False

Data redundancy is used to establish relationships between data but is never used to improve database performance. T/F

False

Database processing programs are coded and tested during the design stage of the systems development life cycle. T/F

False

Databases were developed as the first application of computers to data processing. T/F

False

Generalization is a top-down process. T/F

False

The relational data model does, at the time, directly support subtype.supertype relationships. T/F

False

The steps of the systems development life cycle can only be viewed as a linear process. T/F

False

The term legacy system refers to a newly installed database management system. T/F

False

The total specialization rule states that an entity instance of a supertype is allowed not to belong to any subtype. T/F

False

The truncate table statement in SQL creates a new table. T/F

False

There can be multivalued attributes in a relation. T/F

False

Unlike columns, the rows of a relation may not be interchanged and must be stored in one sequence. T/F

False

When subtypes are overlapping, an additional field must be added to the supertype to act as a discriminator. T/F

False

When transforming a one-to-one relationship, a new relation is always created. T/F

False

When transforming a unary many-to-many relationship to relations, a recursive foreign key is used. T/F

False

When transforming a weak entity, one should create one relation with both the attributes of the strong entity and the attributes of the weak entity. T/F

False

A candidate key is a attribute, or combination of attributes, that uniquely identifies a row in a relation. T/F

True

A cascading delete removes all records in other tables associated with the record to be deleted. T/F

True

Because a purchased data model is extensive, you begin by identifying the parts of the data model that apply to your data modeling situtation. T/F

True

Cost and complexity are just two of the disadvantages of database processing. T/F

True

Data from prior systems is converted to the new systems during the implementation phase of the systems development life cycle. T/F

True

Data structures include data organized in the form of tables with rows and columns. T/F

True

Database maintenance is typically the longest step of the database development process. T/F

True

Enterprise modeling sets the range and general contents of organizational databases. T/F

True

File processing systems have been replaced by database systems in most critical business aplications today. T/F

True

The overlap rule specifies that if an entity instance of the supertype is a member of one subtype, it can simultaneously be a member of two (or more) subtypes. T/F

True

When a regular entity type contains a multivalued attribute, two relations are created. T/F

True

When normalizing, the goal is to decompose relations with anomalies to produce smaller, well-structured relations. T/F

True

You will never need to map data in current databases to data in a package data model. T/F

False

when the total specialization rule is set for a supertype/subtype relationship, one could roughly compare the supertype to an abstract class in object-oriented programming. T/F

False

A universal data model is a generic or template data model that cen be reused as a starting point for a data modeling project. T/F

True

In 1998, ANSI/SPARC published an important document describing the three-schema architecture. T/F

False

In the relational data model, associations between tables are defined through the use of primary keys. T/F

False

It is easy to miss the opportunity to visualize future requirements shown in the full data model when using a packaged data model. T/F

False

Personal databases are designed to support a small group of individuals working together on project. T/F

False

Reduced program maintenance is an advantage of file processing systems. T/F

False

Subtypes at the lowest level of a hierarchy do not inherit attributes from their ancestors. T/F

False

Supertype/subtype relationships should be used when the instances of a subtype participate in not relationships which are unque to that subtype. T/F

False

The entity integrity rule states that a primary key attribute can be null. T/F

False

A completeness contraint may specify that each entity of the supertype must be a member of some subtype in the relationship. T/F

True

A partial functional dependency is a functional dependency in which one or more nonkey atributes are functionally dependent on part (but not all) of the primary key. T/F

True

A subtype can become a supertype if the subtype has other subtypes beneath it. T/F

True

A well-structured relation contains minimal redundancy and allows users to manipulate the relation without errors or inconsistencies. T/F

True

All vaues that appear in a column of a relation must be taken from the same domain. T/F

True

An enterprise data model describes the scope of data for only one information system. T/F

True

In practice, databases today may contain either data or information. T/F

True

The disjointed rules specifies that if an entity instance of the supertype is a member of one subtype, it MUST simultaneaously be a member of another subtype. T/F

False

The physical structure and storage organization of the database are decided upon during the implementation phase of the systems development life cycle. T/F

False

The primary key of the many side migrates to the one side when transforming a one-to-many relationship. T/F

False

With the traditional file processing approach, each application shares data files, enabling much data sharing. T/F

False

A physical schema contains the specifications for how data from a conceptual schema are stored in a computer's secondary memory. T/F

True

A primary key is an attribute that uniquely identifies each row in a relation. T/F

True

A referential integrity constraint is a rule that maintains consistency among the rows of two relations. T/F

True

A relational database establishes the relationships between entities by means of a common field. T/F

True

An entity instance of a subtype represents the same entity instance of the supertype. T/F

True

An extranet uses internet protocols to establish limited access to comapny data by the company's customers and suppliers. T/F

True

Applications built with a multitier architecture are meant to support departments. T/F

True

If an identifier is not assigned, the default primary key for an associative relation consists of the two primary key attributes from the other two relations. T/F

True

In a supertype/subtype hierarchy, attributes are assigned at the highest logical level that is possible in the hierarchy. T/F

True

In prototyping, implementation and maintenance activities are repeated as necessary until the product is correct. T/F

True

Informartion is processed date. T/F

True

Mapping existing data to new data in a packaged data model is useful for developing migration plans. T/F

True

Metadata are data that descrbe the properties of other data. T/F

True

One of the major challenges in a data modeling is to recognize and clearly represent entities that are almost the same. T/F

True

One property of a relation is that each attribute within a relation has a unique name. T/F

True

Prototyping is a type of rapid application development. T/F

True

Redundancy increases the risk of inconsistent data. T/F

True

Specialization is the reverse of generalization. T/F

True

The allowable range of values for a given attribute is part of the domain constraint. T/F

True

The most common way to support a group of individuals who work together on a project or group of similar projects is with a two-tier client/server database. T/F

True

The repository is populated during the analysis phase of the systems development life cycle. T/F

True

The systems development life cycle is the traditional methodology used to develop, maintain, and replace information systems. T/F

True

Unplanned duplicate data files are the rule rather than the exception in file processing systems. T/F

True

View integration is the process of merging relations together. T/F

True


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