Chapter 3 Flashcards
(6 cards)
Describe the relational database model’s logical structure
The relational data model focuses on the logical representation of data and relationships, not physical storage. It is based on a mathematical relation—a two-dimensional table of rows and columns. Data is presented as tables (collections of related entities), offering complete data and structural independence.
Identify the relational model’s basic components and explain the structure, contents, and characteristics of a relational table
Basic components: entities, attributes, relationships, and constraints. A relational table (relation) is a 2D structure of rows (tuples) and columns (attributes). Each row represents an entity occurrence; each column an attribute with a domain of values. Rows and columns order is irrelevant. Each table has keys uniquely identifying rows.
Explain the purpose and components of the data dictionary and system catalog
The data dictionary contains metadata describing all user-created tables, attributes, and relationships, serving as the ‘database designer’s database.’ The system catalog is a detailed system-created dictionary storing all database objects, their creators, access privileges, and structural info. Both terms are often used interchangeably.
Identify appropriate entities and then the relationships among the entities in the relational database model
Entities are persons, places, things, or concepts with unique occurrences. Relationships associate entities and are categorized as one-to-many (1:M), many-to-many (M:N), or one-to-one (1:1). Business rules help identify entities and relationships. Relationships use foreign keys linking tables according to relationship type.
Describe how data redundancy is handled in the relational database model
The relational model minimizes data redundancy and inconsistencies by using foreign keys to link related tables, avoiding repeated data. Normalization further structures tables to eliminate unnecessary redundancy and data anomalies by assigning attributes based on functional dependency.
Explain the purpose of indexing in a relational database
An index is an ordered arrangement of keys and pointers to data locations, improving data retrieval efficiency by avoiding full table scans. Indexes can order data by attributes and support primary key enforcement via unique indexes. Each index relates to one table but a table can have many indexes.
