Podcast
Questions and Answers
What is a primary goal when mapping an ERD to relations?
What is a primary goal when mapping an ERD to relations?
- Minimize null values (correct)
- Omit any constraints present
- Maximize derived attributes
- Increase the complexity of the model
Which of the following steps is performed first in converting an ERD to a logical model?
Which of the following steps is performed first in converting an ERD to a logical model?
- Create derived attributes
- Analyze entity relationships
- Identify complex attributes
- Specify the name of the relation (correct)
What should be included in the list when defining a relation from an ERD?
What should be included in the list when defining a relation from an ERD?
- Simple attributes only (correct)
- All attributes including derived ones
- Only the primary keys
- Complex and derived attributes
Which of the following is not a goal during the mapping of an ERD to relations?
Which of the following is not a goal during the mapping of an ERD to relations?
What is the purpose of maintaining constraints during the mapping process?
What is the purpose of maintaining constraints during the mapping process?
What does the individual relation schemas within a database represent?
What does the individual relation schemas within a database represent?
How many relation schemas are mentioned in the COMPANY database schema?
How many relation schemas are mentioned in the COMPANY database schema?
What is a schema diagram used for in a relational database?
What is a schema diagram used for in a relational database?
Which of these statements is true about relation schemas?
Which of these statements is true about relation schemas?
In the context of databases, what is meant by 'relation'?
In the context of databases, what is meant by 'relation'?
What does mandatory participation on both sides of a 1:1 relationship imply in mapping?
What does mandatory participation on both sides of a 1:1 relationship imply in mapping?
Which approach is NOT a valid option for 1:1 relationships in participation?
Which approach is NOT a valid option for 1:1 relationships in participation?
In a 1:1 relationship with optional participation on both sides, how should you approach mapping?
In a 1:1 relationship with optional participation on both sides, how should you approach mapping?
What is the key requirement when there is mandatory participation on one side of a 1:1 relationship?
What is the key requirement when there is mandatory participation on one side of a 1:1 relationship?
What is the difference between mandatory and optional participation in a 1:1 relationship?
What is the difference between mandatory and optional participation in a 1:1 relationship?
How should a 1:N recursive relationship be represented according to the ER-to-Relational Mapping Algorithm?
How should a 1:N recursive relationship be represented according to the ER-to-Relational Mapping Algorithm?
What additional elements must be included when mapping a unary 1:N relationship?
What additional elements must be included when mapping a unary 1:N relationship?
In the context of a unary 1:N relationship, what does the term 'FK' refer to?
In the context of a unary 1:N relationship, what does the term 'FK' refer to?
Why is one copy of the primary key renamed in the 1:N recursive relationship mapping?
Why is one copy of the primary key renamed in the 1:N recursive relationship mapping?
What does the mapping of unary relationship types involve?
What does the mapping of unary relationship types involve?
What type of entity is referred to by the relation DEPENDENT?
What type of entity is referred to by the relation DEPENDENT?
Which key is NOT a primary key for the relations mentioned?
Which key is NOT a primary key for the relations mentioned?
Which relation corresponds to the primary key DNUMBER?
Which relation corresponds to the primary key DNUMBER?
What does PNUMBER represent in the given context?
What does PNUMBER represent in the given context?
Which entity type does SSN serve as a primary key for?
Which entity type does SSN serve as a primary key for?
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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."
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