4.AbordagemER_Labs2

4.AbordagemER_Labs2 - social security number, or SSN) and...

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Engenharia Informática; Unidade Curricular de Bases de Dados I (2ºAno, 3º Semestre) 11 URL – http://www.estgp.pt/docentes/lopes Docente – Secundino Domingos Marques Lopes (slopes@estgp.pt) [er.11] - A university database contains information about professors (identified by social security number, or SSN) and courses (identified by courseid). Professors teach courses; each of the following situations concerns the Teaches relationship set. For each situation, draw an ER diagram that describes it (assuming that no further constraints hold). 1. Professors can teach the same course in several semesters, and each offering must be recorded. 2. Professors can teach 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.) 3. Every professor must teach some course. 4. Every professor teaches exactly one course (no more, no less). 5. Every professor teaches exactly one course (no more, no less), and every course must be taught by some professor. 6. Now suppose that certain courses can be taught by a team of professors jointly, but it is possible that no one professor in a team can teach the course. Model this situation, introducing additional entity sets and relationship sets if necessary. [er.12] - Consider the following information about a university database: 1. Professors have an SSN, a name, an age, a rank, and a research specialty. 2. Projects have a project number, a sponsor name (e.g., NSF), a starting date, an ending date, and a budget. 3. Graduate students have an SSN, a name, an age, and a degree program (e.g., M.S. or Ph.D.). 4. Each project is managed by one professor (known as the project's principal investigator). 5. Each project is worked on by one or more professors (known as the project's co- investigators). 6. Professors can manage and/or work on multiple projects. 7. Each project is worked on by one or more graduate students (known as the project's research assistants). 8. When graduate students work on a project, a professor must supervise their work on the project. Graduate students can work on multiple projects, in which case they will have a (potentially different) supervisor for each one. 9.
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4.AbordagemER_Labs2 - social security number, or SSN) and...

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