databases question and need the explanation and answer to help me learn.
please answer well
Requirements: please answer well
Question One
In a train stations database, an employee MUST be a train driver, ticket issuer or train attendant, with following constraint: Same employee cannot occupy more than one job type.
Draw EER diagram to represent specialization of employees in the train station database.
Answer:
Question Two
Draw the schema mapping (logical database design) for the following part of ER diagram for train station database. When appropriate use the foreign key option.
Answer
Answer:
Question Three
Suppose you are creating a database for a library management system. Explain how you would create a table for the “books” entity and insert some sample data, and then alter the table to add a new column for the “authorID” attribute and update “authorID” with some data. Finally, write a SQL query to retrieve all the books that were published after the year 2000.
Note that this book schema has several columns, including “book_id” as the primary key, “title”, “authorN”, “publisher”, “publication_year”, “isbn”, “language”, and “num_pages”. It also includes “available” column that is set to “true” by default and can be used to track the availability of the book.
Answer:
Question Four
Write a SQL query that retrieves the names and email addresses of all students who are enrolled in at least one course in the “Computer Science” department and have a graduation year of 2022 or later. Include the course name and instructor name for each enrollment in the output. Schemas of the tables are below.
“students” table:
student_id: unique identifier for the student
name: name of the student
email: email address of the student
major: field of study for the student
graduation_year: expected year of graduation for the student
“courses” table:
course_id: unique identifier for the course
course_name: name of the course
instructor_name: name of the instructor teaching the course.
department: department offering the course.
course_description: description of the course
“enrollments” table:
enrollment_id: unique identifier for the enrollment
student_id: identifier for the student enrolled in the course.
course_id: identifier for the course the student is enrolled in
enrollment_date: date the student enrolled in the course
grade: grade the student received in the course
Answer:
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