Podcast Beta
Questions and Answers
What is a primary goal when mapping an ERD to relations?
Which of the following steps is performed first in converting an ERD to a logical model?
What should be included in the list when defining a relation from an ERD?
Which of the following is not a goal during the mapping of an ERD to relations?
Signup and view all the answers
What is the purpose of maintaining constraints during the mapping process?
Signup and view all the answers
What does the individual relation schemas within a database represent?
Signup and view all the answers
How many relation schemas are mentioned in the COMPANY database schema?
Signup and view all the answers
What is a schema diagram used for in a relational database?
Signup and view all the answers
Which of these statements is true about relation schemas?
Signup and view all the answers
In the context of databases, what is meant by 'relation'?
Signup and view all the answers
What does mandatory participation on both sides of a 1:1 relationship imply in mapping?
Signup and view all the answers
Which approach is NOT a valid option for 1:1 relationships in participation?
Signup and view all the answers
In a 1:1 relationship with optional participation on both sides, how should you approach mapping?
Signup and view all the answers
What is the key requirement when there is mandatory participation on one side of a 1:1 relationship?
Signup and view all the answers
What is the difference between mandatory and optional participation in a 1:1 relationship?
Signup and view all the answers
How should a 1:N recursive relationship be represented according to the ER-to-Relational Mapping Algorithm?
Signup and view all the answers
What additional elements must be included when mapping a unary 1:N relationship?
Signup and view all the answers
In the context of a unary 1:N relationship, what does the term 'FK' refer to?
Signup and view all the answers
Why is one copy of the primary key renamed in the 1:N recursive relationship mapping?
Signup and view all the answers
What does the mapping of unary relationship types involve?
Signup and view all the answers
What type of entity is referred to by the relation DEPENDENT?
Signup and view all the answers
Which key is NOT a primary key for the relations mentioned?
Signup and view all the answers
Which relation corresponds to the primary key DNUMBER?
Signup and view all the answers
What does PNUMBER represent in the given context?
Signup and view all the answers
Which entity type does SSN serve as a primary key for?
Signup and view all the answers
Study Notes
Mapping ERD to Relations
- The text provides a mapping algorithm for converting an Entity Relationship Diagram (ERD) to a logical model.
- The goal is to preserve information, maintain constraints, and minimize null values.
- The mapping process uses relation names followed by a list of simple attributes enclosed in brackets.
- Participation in a relationship is used to determine the mapping approach.
Step 4: Binary 1:1 Relationship Types
- For mandatory participation on both sides, choose one entity and add its primary key and relationship attributes to the other entity.
- The same approach applies for optional participation on both sides.
Step 5: Unary 1:M Relationship Types
- For recursive relationships, create a single relation with two copies of the primary key, one renamed as a foreign key, and includes relationship attributes.
Mapping of Weak Entity Types
- Create a relation for weak entity types, for example, "DEPENDENT" for the weak entity "DEPENDENT."
- The weak entity's primary key is a combination of the identifying owner entity's primary key and a partial key.
- In the given example, "DNUMBER" is the primary key for the weak entity "DEPENDENT."
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz covers the essential concepts and algorithms for mapping Entity Relationship Diagrams (ERDs) to relational models. It emphasizes the preservation of information, the treatment of different relationship types, and how to create relations, particularly for weak entities. Understand the application of primary and foreign keys in various scenarios.
