Mapping ER Diagrams to Relational Databases
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Questions and Answers

What role does the primary key of the owner entity play in a weak entity relationship?

  • It serves as a unique identifier for all entities.
  • It is included as a foreign key in the weak entity table. (correct)
  • It is not necessary for the weak entity relationship.
  • It becomes the primary key of the weak entity.

    • In the mapping of binary M:N relationships, what is the key of the new table created?

  • The key of the new table is the total number of students.
  • The primary key of the new table is the maximum credit hours.
  • The key of the new table is the course name.
  • The key of the new table is the concatenated keys of the two owner entities. (correct)

    • Which attribute defines a weak entity's primary key in the given example?

  • Last_name
  • Dependent_name
  • First_name (correct)
  • Employee_id

    • What is the foreign key in the Dependent entity table in this context?

    <p>Employee_id</p> Signup and view all the answers

    In a binary 1:1 relationship, what should be done to relate the two entities?

    <p>The primary key of Entity A is included in Entity B.</p> Signup and view all the answers

    Which of the following statements is true regarding the Employee and Dependent relationship?

    <p>Each employee can have multiple dependents.</p> Signup and view all the answers

    How is the relationship between Course and Student entities defined in a mapping of binary M:N relationships?

    <p>A student can enroll in multiple courses, and each course can have multiple students.</p> Signup and view all the answers

    What components make up a primary key in a weak entity?

    <p>A partial key combined with the owner's primary key.</p> Signup and view all the answers

    What is the primary key (PK) in the student table?

    <p>Student_id</p> Signup and view all the answers

    Which of the following relationships is typically represented with a foreign key (FK) in a database?

    <p>1:N relationships</p> Signup and view all the answers

    In the case of a recursive 1:N relationship, what should be included in the same table?

    <p>The primary key of the table</p> Signup and view all the answers

    How should M:N recursive relationships be mapped in a database?

    <p>With a separate table for the relationship</p> Signup and view all the answers

    Which statement correctly describes the function of foreign keys in the context of binary relationships?

    <p>They serve as identifiers for primary keys in other tables</p> Signup and view all the answers

    What characterizes a 1:N mapping in entity relationships?

    <p>Multiple entities can relate back to one entity</p> Signup and view all the answers

    What determines the choice between using a separate table and using PK/FK mapping for entity relationships?

    <p>The necessity for additional attributes in the relationship</p> Signup and view all the answers

    In the example of an employee managing another employee, what does the 'Manage_id' represent?

    <p>The identifier of the manager employee</p> Signup and view all the answers

    What is the correct method to map strong entities with atomic attributes?

    <p>Form columns from the atomic attributes in a new table.</p> Signup and view all the answers

    What should be done for entities with composite attributes when mapping to a relational database?

    <p>Form columns from the elementary parts of the composite attributes.</p> Signup and view all the answers

    How should multi-valued attributes be handled when mapping to a relational database?

    <p>Placed in a separate table with the original table's primary key as a foreign key.</p> Signup and view all the answers

    What is required when mapping weak entities?

    <p>A new table is created for each weak entity.</p> Signup and view all the answers

    Which of the following statements about primary keys is true when mapping strong entities?

    <p>The indicated key of the strong entity becomes the primary key of the new table.</p> Signup and view all the answers

    What is the primary characteristic of atomic attributes?

    <p>They cannot be divided and represent a single piece of data.</p> Signup and view all the answers

    When dealing with binary M:N relationships, what is a common approach in mapping?

    <p>A junction table is created to link the two entities.</p> Signup and view all the answers

    Which attribute type requires creating a new table solely for that attribute during mapping?

    <p>Multi-valued attributes</p> Signup and view all the answers

    Study Notes

    Lecture 1: Mapping ER Diagram to a Relational Database

    • The lecture covers mapping Entity-Relationship (ER) diagrams to relational databases.
    • The outline for the mapping process includes: strong entities, weak entities, binary relationships (M:N, 1:1, 1:N), recursive relationships, n-ary relationships and mapping generalizations/specializations.

    M1. Map Strong Entities

    • Create a new table for each strong entity.
    • Use the entity's primary key as the table's primary key.
    • Choose one candidate key if multiple exist.
    • Attributes are categorized as: atomic, composite, and multi-valued.

    M1.A. Atomic Attributes

    • Create a column for each atomic attribute in the table.

    M1.B. Composite Attributes

    • Create columns from the elementary parts of the composite attribute.

    M1.C. Multi-valued Attributes

    • Create a separate table for the multi-valued attribute.
    • Include the primary key from the original table as a foreign key.
    • The new table's key is the primary key.

    M2. Map Weak Entities

    • Create a new table for each weak entity.
    • Follow the same steps as M1.
    • Include the primary key of the owner entity as a foreign key in the weak entity table.
    • The partial key of the weak entity becomes the primary key.

    M3. Map Binary M:N Relationships

    • Create a new table for each M:N relationship.
    • Include the primary keys of both entities as foreign keys.
    • The concatenated foreign keys of both entities represent the primary key in the new table.

    M4. Map Binary 1:1 Relationships

    • Include the primary key of entity A as a foreign key into entity B (the relationship).

    M5. Map Binary 1:N Relationships

    • Most 1:N relationships are mapped using the primary-key/foreign-key method.
    • A separate table can also be created following M3 rules.

    M6. Map Recursive Relationships

    • For 1:N recursive relationships, re-include the primary key of the table into the same table to establish the recursive relationship.
    • For M:N recursive relationships, create a separate table for the relationship.

    M7. Map n-ary Relationships

    • Create a new table for each n-ary relationship.
    • Include all attributes of the relationship in the table.
    • Use the keys of the connected entities as foreign keys, combining them for the primary key of the new table.

    M8. Map Generalizations/Specializations

    • Create one table for the generalization entity and one for each specialization entity.

    • Place attributes for each entity in its corresponding table.

    • Include the primary key of the generalization entity in the specialization entity table.

    • This is an example of an ERD:

      • A person can be an employee or a customer.
      • An employee can be an officer, teller, or secretary.
      • Each has specific attributes.

    Summary of Mapping Constructs and Constraints

    • This table summarizes the correspondence between ER and relational models.
      • ER model elements (entity type, relationship type, attributes) and their relational model counterparts (Entity relation, foreign key, attribute, relationship relation) are listed.

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    Lecture 1: Mapping ER Diagram to Relational Database PDF

    Description

    This quiz covers the process of mapping Entity-Relationship (ER) diagrams to relational databases, focusing on strong and weak entities, as well as binary and recursive relationships. It delves into the creation of tables for different types of attributes, including atomic, composite, and multi-valued attributes. Test your knowledge on these key concepts in database design!

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