w2-aziz-databases #41
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Week2/Relationships.js
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| paper_title VARCHAR(255) NOT NULL, | ||
| conference VARCHAR(255), | ||
| publish_date DATE, | ||
| author_id INT, |
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This approach only allows a research paper to have one author, but in real life research papers usually have multiple authors. Can you modify the code to support a many-many relationship between papers and authors?
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PRIMARY KEY (paper_id, author_id),
i added primary key. i think it will be solve the problem.
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A primary key that includes author_id and paper_id doesn't still doesn't support the many-to-many relationship without having many duplicate rows. to support a many-to-many relationship you need to create a relationship table that only contains two fields: paper_id and author_id
Here's some reading on that that might help
https://www.geeksforgeeks.org/relationships-in-sql-one-to-one-one-to-many-many-to-many/#:~:text=3.%20Many%2Dto%2DMany%20Relationship
Week2/Relationships.js
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| const authorId = Math.floor(Math.random() * 15) + 1; // Random author_id between 1 and 15 | ||
| papers.push([ | ||
| `Research Paper ${i}`, | ||
| `Conference ${i}`, | ||
| `2023-01-${i}`, | ||
| authorId, | ||
| ]); |
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Nice, this is a really elegant way to create test data
| console.log("Authors and their Mentors:"); | ||
| console.table(authorsWithMentors); | ||
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| // 2. Authors and their published papers |
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Great job fixing the many-to-many relationship! Now queries 2,3,4, and 6 need to be updated to support your the new schema. Remember that research_papers table no longer has an author_id field
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| // 4. Sum of the research papers published by all female authors | ||
| const femaleAuthorsPapersCountQuery = ` | ||
| SELECT COUNT(*) AS FemaleAuthorsPapers |
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Careful that you don't double count papers that have multiple female authors. To handle that you can use the DISTINCT keyword as in COUNT(DISTINCT(ap.paper_id))
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| // 6. Sum of the research papers of the authors per university | ||
| const sumPapersPerUniversityQuery = ` | ||
| SELECT a.university, COUNT(ap.paper_id) AS TotalPapers |
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Here as well you need to avoid double counting the same paper if it had multiple authors that are from the same university
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