Week 2 database Elias #26
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…nstead of nested callbacks. This makes the code easier to read and maintain. I added a foreign key constraint for the invited_by field in the Invitee table. This ensures that each person invited actually exists in the table, improving data integrity. I updated how we manage the database connection to use promises, which makes it easier to handle errors that may occur. I also improved the comments in the code to make it clearer how we set up the database and create the tables.
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Hello Elias,
There are some comments which need rework. The main point is about the relationship between papers and authors. Thus relevant queries in exercise 3 and 4 need rework too.
Feel free to contact me on slack if you have any questions. Keep fighting! 💪
| paper_title VARCHAR(255) NOT NULL, | ||
| conference VARCHAR(255), | ||
| publish_date DATE, | ||
| author_id INT, |
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Needs work: one paper can have several authors. Single author_id column in paper table can only refer to one author. Try to find another way to reflect the relationship between authors and papers.
Week2/assignment/joins.js
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| const queryAuthorsAndPapers = ` | ||
| SELECT a.*, rp.paper_title | ||
| FROM authors a | ||
| LEFT JOIN research_papers rp ON a.author_id = rp.author_id;`; |
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Needs work: as mentioned in another comment, the table structure needs to be changed to reflect the correct relationship between authors and papers. Hence the relevant queries need rework too.
Week2/assignment/aggregate.js
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| SELECT rp.paper_title, COUNT(a.author_id) AS number_of_authors | ||
| FROM research_papers rp | ||
| LEFT JOIN authors a ON rp.author_id = a.author_id | ||
| GROUP BY rp.paper_id;`; |
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Needs work: as mentioned in another comment, the table structure needs to be changed to reflect the correct relationship between authors and papers. Hence the relevant queries need rework too.
Week2/assignment/aggregate.js
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| const queryFemalePapersCount = ` | ||
| SELECT COUNT(*) AS total_female_papers | ||
| FROM research_papers rp | ||
| JOIN authors a ON rp.author_id = a.author_id | ||
| WHERE a.gender = 'Female';`; |
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Needs work: as mentioned in another comment, the table structure needs to be changed to reflect the correct relationship between authors and papers. Hence the relevant queries need rework too.
Week2/assignment/aggregate.js
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| // Query for sum of research papers of authors per university | ||
| const queryTotalPapersPerUniversity = ` | ||
| SELECT a.university, COUNT(rp.paper_id) AS total_papers | ||
| FROM authors a | ||
| LEFT JOIN research_papers rp ON a.author_id = rp.author_id | ||
| GROUP BY a.university;`; |
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Needs work: as mentioned in another comment, the table structure needs to be changed to reflect the correct relationship between authors and papers. Hence the relevant queries need rework too.
Week2/assignment/aggregate.js
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| connection.query(queryMinMaxHIndex, (error, results) => { | ||
| if (error) throw error; | ||
| console.log('Min and Max H-index per university:', results); | ||
| }); |
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suggestion: these lines are repeated several times. Only the query and the log message are different. You can extract these lines into a separate function which accepts log message and query as parameters. Always keep DRY principle (don't repeat yourself) in mind when you are coding.
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