Database Mapping

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the first step in the ER-to-Relational Mapping Algorithm?

  • Mapping of N-ary Relationship Types
  • Mapping of Regular Entity Types (correct)
  • Mapping of Multivalued attributes
  • Mapping of Binary 1:1 Relation Types

What is the purpose of Step 1 in the ER-to-Relational Mapping Algorithm?

  • To map multivalued attributes
  • To map weak entity types
  • To create a relation with all the simple attributes of the entity type (correct)
  • To map binary 1:1 relation types

What is chosen as the primary key for the relation R in Step 1?

  • One of the key attributes of E (correct)
  • A multivalued attribute of E
  • A composite attribute of E
  • Any simple attribute of E

What happens if the chosen key of E is composite in Step 1?

<p>The set of simple attributes form the primary key (B)</p> Signup and view all the answers

What is created in Step 2 for each weak entity type W?

<p>A relation with all the simple attributes of W and foreign key attributes of the owner entity type (A)</p> Signup and view all the answers

What are included as foreign key attributes of the relation R in Step 2?

<p>The primary key attribute(s) of the relation(s) corresponding to the owner entity type(s) (C)</p> Signup and view all the answers

What is the purpose of Steps 8 and 9 in the ER-to-Relational Mapping Algorithm?

<p>To map specialization or generalization and union types (B)</p> Signup and view all the answers

What is the result of mapping the COMPANY ER schema into a relational schema?

<p>The creation of three relations: EMPLOYEE, DEPARTMENT, and PROJECT (B)</p> Signup and view all the answers

What is the primary key of the DEPENDENT relation?

<p>{ESSN, DEPENDENT_NAME} (B)</p> Signup and view all the answers

Which approach is used to map a binary 1:1 relationship type?

<p>Foreign Key approach (B)</p> Signup and view all the answers

What is the purpose of Step 2 in mapping ER schema to relational schema?

<p>Mapping of Weak Entity Types (C)</p> Signup and view all the answers

What is the primary key of the relation DEPENDENT renamed to?

<p>ESSN (D)</p> Signup and view all the answers

Which entity type is chosen to serve in the role of S in a 1:1 relationship type?

<p>Entity type with total participation (A)</p> Signup and view all the answers

In a binary 1:N relationship type, where is the foreign key included?

<p>In the relation S (A)</p> Signup and view all the answers

What is included as attributes of S in a 1:N relationship type?

<p>Simple attributes of the 1:N relation type (A)</p> Signup and view all the answers

What is the result of mapping the COMPANY ER schema?

<p>A relational schema (C)</p> Signup and view all the answers

What is the primary key of R in the given ER model?

<p>{DNUMBER, DLOCATION} (C)</p> Signup and view all the answers

What is created to represent an n-ary relationship type R, where n>2?

<p>A new relationship S (D)</p> Signup and view all the answers

What is included as attributes of S in the mapping of an n-ary relationship type?

<p>All of the above (D)</p> Signup and view all the answers

What is the primary key of the relation SUPPLY in the relational schema?

<p>{SNAME, PARTNO, PROJNAME} (A)</p> Signup and view all the answers

What corresponds to a 'Relationship' relation in the relational model?

<p>All of the above (D)</p> Signup and view all the answers

What is mapped to a set of simple component attributes in the relational model?

<p>Composite attribute (C)</p> Signup and view all the answers

What is the mapping for a multivalued attribute in the relational model?

<p>Relation and foreign key (B)</p> Signup and view all the answers

What is the next step after mapping an n-ary relationship type?

<p>Options for Mapping Specialization or Generalization (C)</p> Signup and view all the answers

What is the primary key of the WORKS_ON relation in the relational database schema?

<p>The combination of ESSN and PNO (A)</p> Signup and view all the answers

What is the purpose of including the primary key DNUMBER of the DEPARTMENT relation as a foreign key in the EMPLOYEE relation?

<p>To represent the M:N relationship type WORKS_FOR (A)</p> Signup and view all the answers

What is included in the relation S to represent the M:N relationship type R?

<p>The primary keys of the participating entity types and any simple attributes of the M:N relationship type (B)</p> Signup and view all the answers

What is the primary key of the relation R created to map a multivalued attribute A?

<p>The combination of A and K (D)</p> Signup and view all the answers

Why is the attribute DLOCATION included in the relation DEPT_LOCATIONS?

<p>To represent the multivalued attribute LOCATIONS of DEPARTMENT (D)</p> Signup and view all the answers

What is the purpose of creating a new relation S to represent a binary M:N relationship type R?

<p>To create a relation between the participating entity types (D)</p> Signup and view all the answers

What is the primary key of the DEPT_LOCATIONS relation?

<p>The combination of DLOCATION and DNUMBER (A)</p> Signup and view all the answers

What is the main difference between Options 8A and 8B?

<p>Option 8A creates a single relation for the superclass, while Option 8B creates a relation for each subclass. (D)</p> Signup and view all the answers

What is the purpose of creating a relation L in Option 8A?

<p>To store the attributes of the superclass. (A)</p> Signup and view all the answers

What is common in the attributes of relations Li in Options 8A and 8B?

<p>They all have the attribute k. (B)</p> Signup and view all the answers

What is the limitation of using Option 8B?

<p>It can only be used for total specialization. (B)</p> Signup and view all the answers

What is the advantage of using Option 8C?

<p>It requires less relations to be created. (C)</p> Signup and view all the answers

What is the purpose of the attribute t in Option 8C?

<p>To store the type of the entity. (A)</p> Signup and view all the answers

Which option is suitable for mapping partial specialization?

<p>Option 8A (A)</p> Signup and view all the answers

What is the primary key of the relation L in Option 8C?

<p>{k} (B)</p> Signup and view all the answers

Flashcards are hidden until you start studying

Study Notes

ER-to-Relational Mapping Algorithm

  • The algorithm consists of 9 steps to map ER diagrams to relational schemas
  • Steps 1-7 map ER model constructs to relations
  • Steps 8-9 map EER model constructs to relations

Step 1: Mapping of Regular Entity Types

  • For each regular entity type E, create a relation R with all simple attributes of E
  • Choose a key attribute of E as the primary key for R
  • If the chosen key is composite, the set of simple attributes that form it will together form the primary key of R

Step 2: Mapping of Weak Entity Types

  • For each weak entity type W, create a relation R with all simple attributes of W
  • Include the primary key attribute(s) of the owner entity type(s) as foreign key attributes of R
  • The primary key of R is the combination of the primary key(s) of the owner(s) and the partial key of W, if any

Step 3: Mapping of Binary 1:1 Relation Types

  • For each binary 1:1 relationship type R, identify the relations S and T that correspond to the entity types participating in R
  • Choose one of the relations, say S, and include a foreign key in S, the primary key of T
  • It is better to choose an entity type with total participation in R

Step 4: Mapping of Binary 1:N Relationship Types

  • For each regular binary 1:N relationship type R, identify the relation S that represents the participating entity type at the N-side of the relationship type
  • Include as foreign key in S the primary key of the relation T that represents the other entity type participating in R
  • Include any simple attributes of the 1:N relation type as attributes of S

Step 5: Mapping of Binary M:N Relationship Types

  • For each regular binary M:N relationship type R, create a new relation S to represent R
  • Include as foreign key attributes in S the primary keys of the relations that represent the participating entity types
  • Also, include any simple attributes of the M:N relationship type as attributes of S

Step 6: Mapping of Multivalued Attributes

  • For each multivalued attribute A, create a new relation R
  • R includes an attribute corresponding to A, plus the primary key attribute K as a foreign key in R
  • The primary key of R is the combination of A and K

Step 7: Mapping of N-ary Relationship Types

  • For each n-ary relationship type R, create a new relation S to represent R
  • Include as foreign key attributes in S the primary keys of the relations that represent the participating entity types
  • Also, include any simple attributes of the n-ary relationship type as attributes of S

Mapping EER Model Constructs to Relations

  • Step 8: Options for mapping specialization or generalization
  • Step 9: Mapping of union types (categories)

Step 8: Options for Mapping Specialization or Generalization

  • Option 8A: Multiple relations - superclasses and subclasses
  • Option 8B: Multiple relations - subclass relations only
  • Option 8C: Single relation with one type attribute
  • Option 8D: Single relation with multiple type attributes

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team
Use Quizgecko on...
Browser
Browser