Limitations of a file system in data management - ANSWER: Data reliance
- Structural dependence
- Data redundancy causes deletion, insertion, and modification anomalies.
Hardware, software, people, procedures, and data are the components of a
database management system (DBMS) environment.
Data Modeling: ANSWER is iterative and progressive.
Database Models - Conceptual and Implementation
Conceptual - ANSWER The conceptual model provides a comprehensive
picture of a database. Describes the major data objects while avoiding specifics,
and defines their relationships.
Entities and relationships, many kinds of relationships
Implementation - ANSWER hierarchical, network, relational, object-oriented.
-It does sustain many, many relationships.
Hierarchical: ANSWER upside-down tree structure, 1-M relationship.
-Easy to grasp, but downsides include no standards and data reliance.
Network--ANSWER upside-down tree topology, supports M-M relationships.
- standards, but data reliance, difficult to implement because of the many to
many.
Object Oriented: ANSWER data becomes an active component of the system
via methods and properties.
,-You can leverage code reuse, polymorphism, and encapsulation in the
database.
Relational: - ANSWER remains the most popular database model.
Different levels of data models: conceptual, internal, external, and physical.
Conceptual Database Model - The result of the conceptual design process. The
conceptual model offers a comprehensive perspective of the complete database.
Describes the key data elements while avoiding specifics.
-highest level, has the least amount of detail, and is not dependent on hardware
or software.
Internal Database Model - ANSWER refers to a degree of data abstraction that
converts the conceptual model into a specific DBMS model for implementation.
-Adapt the conceptual model to the database that has been chosen.
External Database Model - ANSWER The application programmer's
perspective on the data environment. Because of its business unit focus, an
external model works with a subset of the global database schema.
-both are software-reliant and provide a decomposition of the model into
functional parts.
Physical Database Model - An ANSWER model that describes the physical
aspects of the data (location, path, and format). It is both hardware and software
dependant.
-Planning how to get to data, access pathways,
, Entities, attributes, tables, rows, columns, attribute domain, cardinality, and
connectivity are the fundamental principles of the relational database paradigm.
Entity - The person, place, or thing about which you want to store data
(expressed as a table or relation).
+represented by a rectangle.
Attributes are the characteristics or properties of data or entities that are stored
in columns.
+ symbolized by ovals.
+ property of an entity and kept in a table.
• Each row in the row table represents an instance of an entity.
+ represents a record in a file.
• Column ANSWER represents the attribute.
+ represents a field in a file.
• Attribute domain: ANSWER indicates the possible range of values.
• Cardinality - ANSWER Indicates the minimum and maximum number of
entity occurrences connected with one.
occurrence of related entities (similar to a range)
• Connectivity - ANSWER describes the relationship classification (type).