Data Modelling & ER - Lecture 2

Practice flashcards covering the data modeling life cycle, database design phases, ER model elements, cardinalities, relationship degrees, and ER notation conventions.

What are the three main phases of database design?

Conceptual database design, Logical database design, and Physical database design.

What engineering principle guides the phases of database design?

Separating the decisions relating to what to represent (or store) in the database from those relating to how to do it.

What is Conceptual Database Design?

The first phase of database design, which involves creating a conceptual data model from users' requirements that is independent of implementation details such as target DBMS software and hardware platform.

What is Logical Database Design?

The second phase of database design, which involves creating a logical data model based on the target data model of the DBMS (such as the relational model) from the conceptual data model.

What is Physical Database Design?

The third and final phase of database design, which involves implementing the database tailored to a specific DBMS software (such as Oracle, PostgreSQL, MySQL, SQLite, or MS-Access).

What is an Entity Relationship Model?

A graphical representation of the entire database system used as a DBMS- and hardware-independent design and planning tool, composed of entities, attributes, and relationships.

What is an entity in an Entity Relationship Model?

Any object in the system that we want to model and store information about, usually representing real-world objects and expressed as nouns.

What is an attribute in an Entity Relationship Model?

A property of an entity where all data relating to that entity is stored, with each attribute taking values from its specific domain (data type).

What is a relationship in an Entity Relationship Model?

A meaningful association or logical link between entities, usually represented by verbs.

What ERD diagram styles are identified in the lecture?

Chen, Bachman, UML, and Crow's Foot.

How are entities, attributes, and relationships depicted in a Crow's Foot ERD?

Entities are represented by rectangles, attributes are listed inside the entity box, and relationships are represented by lines.

What is the degree of a relationship in ER modeling?

The number of participating entity types involved in a relationship.

What is a unary or recursive relationship?

A relationship where only one entity type is involved (for example, Employee manages Employee).

What rule applies to ternary relationships in an E-R model?

Ternary relationships should always be removed before finishing the model.

What are the three cardinalities of relationships in database design?

One to One (1:1), One to Many (1:M), and Many to Many (M:N).

How are Many to Many (M:N) relationships resolved in ER diagrams?

They are replaced using an intermediate entity that is revealed by breaking down the many-to-many relationship.

In Kendall & Kendall notation, what do the Associative entity and Attributive entity symbols represent?

An associative entity (a box containing a diamond) is used to join two entities, and an attributive entity (a rounded rectangle with diagonal lines in corners) is used for repeating groups.

In Kendall & Kendall relationship notations, what do line terminals with circles indicate?

A line ending with a circle and hash mark represents a 'To 0 or 1 relationship' (Only zero or one), while a line ending with a circle and crow's foot represents a 'To 0 or more relationship' (Can be zero, one, or more).

In ER diagrams that list attribute lists alongside entity shapes, how is the primary key indicated?

The key attribute name is underlined.