DB Mang Ch.2

Composite attribute

(...), address

Weak Entity

Entity whose instances cannot exist in the database without the existence of an instance of another entity, lacks a unique identifier, and is double-lined.

Data guidelines

Guidelines provide a concise description of essential data meaning accompanied by diagrams.

Data Modeling

Identify facts that must be stored in a database, the first step in the design of a database solution.

Cardinality Constraints

Includes optional one, mandatory one, optional many, and mandatory many constraints.

Associative Entity

An entity type that associates instances of one or more entity types and contains attributes peculiar to the relationship between those entity instances.

Importance of Data Modeling

Characteristics of data, facts, and rules captured during data modeling are essential in assuring data integrity.

Business Rules

Defines relationship rules that specify a relationship between two pieces of data.

Entity instance

Entity instance is a single occurrence of an entity type.

Entity

Entity is a person, place, object, event, or concept for which information should be recorded and retained. Many instances w/ multiple attributes

Strong Entity

Entity that exists independently of other entity types, has a unique identifier, and is single-lined.

ERD Symbology

Entity types (3), Relationship degrees (3), Relationship cardinality (4), Attributes (6).

Good data name

Meaningful, unique, readable, repeatable, related to business characteristics

Attributes

Property or characteristic of an entity or relationship type.

Good Data Models

Well-formed (descriptive names) high fidelity (modeling the real world accurately)

Derived attribute

[attribute], total cost

Entity type

collection of entities that share common properties.

Associative entity

combination of relationship and entity, associates the instances of one more more entity types and contains attributes, create when many to many relationships, ternary relationship

Relationship instances

exist between specific entity instances.

Simple attribute

first name, city

Modeling process

first step is to design the DB solution (conceptual model)

Relationship Types

modeled as lines between entity types.

Data definitions: fact

refers to a measurable event, an association between two or more terms.

Data Definitions: term

refers to a word or phrase with a specific meaning used to define a component or concept within a database structure.

Relationship Degree

refers to the number of entity types participating in the relationship (unary, binary, ternary).

Qualities of good data

relevant, quality/quantity, structured, standardized, and analytics-ready data.

Relationship cardinality

specifies how many of each entity type are allowed (one-to-one, one-to-many, many-to-many).

Identifier attribute

underlined once

Multi-value attribute

{...}, languages spoken, major