Explain the following terms briefly: attribute, domain, entity, relationship, entity set, relationship set, one-to-many relationship

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Questions:

1- Explain the following terms briefly: attribute, domain, entity, relationship, entity set, relationship set, one-to-many relationship, many-to-many relationship, participation constraint, overlap constraint, covering constraint, weak entity set, aggregation, and ISA relationships. (14 pts)

2- A company database needs to store information about employees (identified by EID, with salary and phone as attributes); departments (identified by DID, with dname and budget as attributes); and children of employees (with name and age as attributes). Employees work in departments; each department is managed by an employee; a child must be identified uniquely by name when the parent (who is an employee; assume that only one parent works for the company) is known. We are not interested in information about a child once the parent leaves the company. Draw an ER diagram that captures this information. (13 pts)

3- A university database contains information about professors (identified by a unique id called PID) and courses (identified by CID). Professors offer courses; each of the following situations concerns the Offers relationship set.

For each situation, draw a separate ER diagram that describes it (assuming that no further constraints hold). (16 pts)

● Professors can offer the same course in several semesters, and each offering must be recorded.

● Professors can offer the same course in several semesters, and only the most recent such offering needs to be recorded. (Assume this condition applies in all subsequent questions.)

 

● Every professor offers exactly one course (no more, no less).

● Every professor offers exactly one course (no more, no less), and every course must be offered by some professor.

● Every professor must offer some courses.

● Now suppose that certain courses can be offered by a team of professors jointly, but it is possible that no one professor in a team can offer the course. Model this situation, introducing additional entity sets and relationship sets if necessary.

 

4- Consider the following information about a university database:

● Professors have a unique id (PID), a name, an age, a rank, and a research field.

● Projects have a project number (PID), a sponsor name (e.g., NSF), a starting date, an ending date, and a budget.

● Graduate students have an GSID, a name, an age, and a degree program (e.g., M.S. or Ph.D.).

● Each project is managed by one professor (known as the project’s principal investigator).

● Each project is handled on by one or more professors (known as the project’s co- investigators).

● Professors can manage and/or work on multiple projects.

● Each project is handled on by one or more graduate students (known as the project’s research assistants).

● When graduate students handle a project, a professor must supervise their work on the project.

● Graduate students can handle multiple projects, in which case they will have a (potentially different) supervisor for each one.

● Departments have a department number, a department name, and a main office.

● Departments have a professor (known as the chairman) who runs the department.

● Professors work in one or more departments, and for each department that they work in, a time percentage is associated with their job.

● Graduate students have one major department in which they are working on their degree.

● Each graduate student has another, more senior graduate student (known as a student advisor) who advises him or her on what courses to take.

 

Design and draw an ER diagram that captures the information about the university. Be sure to indicate any key and participation constraints. (17 pts)

 

5- A company named Notown Records has decided to store information about musicians who perform on its albums (as well as other company data) in a database. The company has wisely chosen to hire you as a database designer (at your usual consulting fee of $2,500/day).

● Each musician that records at Notown has an MID, a name, an address, and a phone number. Poorly paid musicians often share the same address, and no address has more than one phone.

● Each instrument that is used in songs recorded at Notown has a name (e.g., guitar, synthesizer, flute) and a musical key (e.g., C, B-flat, E-flat).

● Each album that is recorded on the Notown label has a title, a copyright date, a format (e.g., CD or MC), and an album identifier (AID).

● Each song recorded at Notown has a name and an author.

 

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