Oleksandr starshynov w2 databases #20

aleksandrstarshynov · 2025-06-04T11:33:55Z

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RHSebregts

Hi,

Once again sorry for taking so long. I'm afraid there is still some work, or at the very least some clarifying to do here. The structure/naming of the files made it a bit harder to work on, and some interesting decisions have been made.
I'd encourage you to experiment with different drivers, database forms and other things, but it might also cause a lack of focus and polish. If you can do a bit of a cleanup this will all be fine, but it makes it a bit harder to get insights into why you made certain choices and what level of understanding you have.
Feel free to reach out!

RHSebregts · 2025-06-04T20:02:35Z

Week2/Assignment/create_authors_table.js

@@ -0,0 +1,21 @@
+const sqlite3 = require('sqlite3').verbose();


a new week, a new package! Or strictly speaking another DB format. Please, tell me more!
I'm not in love with it yet, I see the return to callback functions over a nice asynchronous approach as a bit of a regression, but I'm ready to be convinced otherwise.

You mean that if we have Promises and async functions already, why I am using SQLite3 and specifically the callback-style API? Good question. The answer is: I do not know. I feel that sometimes curriculum is not up to date and try to find what the most usable staff in the current moment. I like callbacks, we use them a lot in API.

Let me first say that it is good to be curious and look at what's out there. It's a good skill to have as a developer and it will serve you well in your career. One of the most difficult parts of this curiosity, especially in a field that we're still exploring, is knowing what and why things are done a certain way. And that it can distract from getting down the fundamentals.
In this case, your curiosity killed the cat a bit. SQLite and MySQL are not interchangeable and serve quite different purposes. In this case it's ok, since we are using a small data set, but for bigger projects it will have big limitations. It was also just not the assignment.

Allow me an analogy: Let's say that what HYF is trying to do is teaching you how to cook in the French style. And if you want to be a good cook, you need to know the basics in order to know what to look out for when you start developing your own recipes. There are other cuisines that might be more to our tastes, but knowing a single way of cooking first (French in this case) will allow us to use pick up the other techniques better because we understand the fundamentals. The cuisine itself doesn't matter much here, more the fact that we pick one for now and stick with it.

I agree, MySQL is old and creaky, and I don't care much for it either, but it is still running the world and used at basically every company apart from the hippest of startups. And even those will often have a relational db somewhere, just to make sure people don't go crazy.

Callbacks are amazing, and super fun and powerful, but with database queries (especially when they start to depend on each other) they tend to lead to callback hell, which we try to avoid.

RHSebregts · 2025-06-04T20:05:00Z

Week2/Assignment/create_authors_table.js

+      author_name TEXT,
+      university TEXT,
+      date_of_birth TEXT,


Does this TEXT type guarantee anything about values being null?

oh, gash, my bad. In parallel with assignment I have created local db and code and tried to use, test, etc. And I made all fields as non-requider and expecting text, to make my test easier. Sorry, I totally forget to change it back. For sure we have to use VARCHAR(n) or TEXT, DATE for the date_of_birth and NOT NULL. I will update the assignment

RHSebregts · 2025-06-04T20:06:02Z

Week2/Assignment/add_mentor_column.js

@@ -0,0 +1,42 @@
+const sqlite3 = require('sqlite3').verbose();
+
+const db = new sqlite3.Database('example.db');


example.db?

RHSebregts · 2025-06-04T20:06:35Z

Week2/Assignment/add_mentor_column.js

+  });
+
+  db.run(`
+    PRAGMA foreign_keys = OFF;


What does this do?

we work with relational database here. It means that we have under the hood check that we have everything we heeb for the key on the both sides. If we have a key, we check that we have "part" of it in both tables. I guess that by using PRAGMA foreign_keys = OFF we switch-off the check

Ah, I have never worked with SQLite and just really don't know what this PRAGMA stands for. Normally I would look it up myself, but since we're both here to learn I'd love to know if you can find out what the PRAGMA does.

RHSebregts · 2025-06-04T20:07:33Z

Week2/Assignment/add_mentor_column.js

+      CREATE TABLE authors_new (
+        author_id INTEGER PRIMARY KEY,
+        author_name TEXT,
+        university TEXT,
+        date_of_birth TEXT,
+        h_index INTEGER,
+        gender TEXT,
+        mentor INTEGER,
+        FOREIGN KEY (mentor) REFERENCES authors(author_id)


Wait, I thought we already made this table in create_author_table.js? Why are we filling in all it's information again?

Good question. I stuck here during the coding. In Postgres we asielly able to add new column with foreign key ALTER TABLE authors ADD COLUMN mentor INTEGER REFERENCES authors(author_id);
But with SQLite we create a new tablewith the same columns as old one, plus we are including the new column with a foreign key constraint. Then we need to drop existing table and rename the new table. So it replaces the old one and all code that works with the table still able to be linked.
If I found the long way and the way shorted is exist, please show me.

I refuse to believe that we cannot alter a table in SQLite like we can in MySQL, let's look at this together!

https://www.sqlite.org/lang_altertable.html

RHSebregts · 2025-06-04T20:17:22Z

Week2/Assignment/joins.js

+
+try {
+  // Выбираем базу данных
+  await connection.query("USE w2_assignment");


Coming from the other files, does this collection exist?

RHSebregts · 2025-06-04T20:17:51Z

Week2/Assignment/joins.js

+
+  // 📌 Запрос 1: Авторы и их менторы
+  const [authors_mentors] = await connection.query(`
+    SELECT a.author_name AS Author, m.author_name AS Mentor, a.mentor AS "Mentor ID"


RHSebregts · 2025-06-04T20:19:11Z

Week2/Assignment/joins.js

+    FROM authors AS a
+    LEFT JOIN authorPapers AS ap ON a.author_id = ap.author_id
+    LEFT JOIN research_Papers AS rp ON rp.paper_id = ap.paper_id
+    ORDER BY a.author_id


Why would we order on author_id, would users want to do that?

I do not know. It that moment it find this as a good idea. But after your question I see that in real world users will use another column for filtering and ordering. Make no sence in this assignment to order by ID, I agree wth you.

RHSebregts · 2025-06-04T20:20:20Z

Week2/Assignment/aggregates.js

+try {
+  await connection.query("USE w2_assignment");
+
+  // 1. Все статьи и количество авторов


Dit maakt het niet echt makkelijker voor mij om te lezen wat hier staat.

Ik ben het met je eens. Als we internationale regels gebruiken, moet ik Engels gebruiken in de opmerkingen of tips in de code.
I will update tips during the code update, sorry.

RHSebregts · 2025-06-04T20:21:14Z

Week2/Assignment/aggregates.js

+    JOIN 
+      authorPapers ap ON a.author_id = ap.author_id
+    WHERE 
+      a.gender = 'Female';


Since we can add all possible text in this field, will this get us all variations (writing wise) of Female?

You mean that if we have more then one way to write the word in values of the column, by running my code we will get only one type? Make sence. However, I think that better not to give users opportunity to write in, but schoose from the dropdown. In this case we have always only one type, one variation.
From the expirience perspective, is it better everytime to be sure that we code all variation, or we may trast system and specification?

I like your suggestion, but it makes our database very dependent and coupled to a specific frontend. Let's say we also expose this through an API where someone can arbitrarily type "mAle" of "FEMAle"? I would always try and keep in mind whether or not you want to be case-sensitive or insensitive. So here, I think we can do something with the LIKE keyword to negate that.

aleksandrstarshynov · 2025-06-07T06:06:00Z

structure/naming of the files made it a bit harder to work on, and some interesting decisions have been made.
I'd encourage you to experiment with different drivers, database forms and other things, but it might also cause a lack of focus and polish. If you can do a bit of a cleanup this will all be fine, but it makes it a bit harder to get insights into why you made certain choices and what level of understanding you have.
Feel free to reach out!

I think that I have two problems in this module. First is a lack of time, we got mysql, next week nosql... I have not mix but the real mash in my head. And the second issue is that I am not able to remember the sql sintax. Evrry time i have to google or ask chat. Maybe because of this I try not to play with different approaches or structures for the databases. PostrgeSQL and relational databases is more interesting for me. However, in my side project I set up and usinf both.

RHSebregts · 2025-06-07T10:23:34Z

I think that I have two problems in this module. First is a lack of time, we got mysql, next week nosql... I have not mix but the real mash in my head. And the second issue is that I am not able to remember the sql sintax. Evrry time i have to google or ask chat. Maybe because of this I try not to play with different approaches or structures for the databases. PostrgeSQL and relational databases is more interesting for me. However, in my side project I set up and usinf both.

Once again, I admire that you are trying to do a lot, but I think you can help yourself by focussing a bit more on deepening your knowledge as opposed to widening it too much now. I feel that, by now, you should start to get to a stage where you have those SQL queries in your toolbelt. If not, you should first get that down, since they are really fundamental, also for Postgres and other DBs. But also, having to google them is natural and I still need to do that with anything beyond the basics as well.

Also you say Postgres and relational databases are more interesting to you, but it seems to me that MySQL is pretty much the OG relational database.

aleksandrstarshynov · 2025-06-07T13:52:45Z

I think that I have two problems in this module. First is a lack of time, we got mysql, next week nosql... I have not mix but the real mash in my head. And the second issue is that I am not able to remember the sql sintax. Evrry time i have to google or ask chat. Maybe because of this I try not to play with different approaches or structures for the databases. PostrgeSQL and relational databases is more interesting for me. However, in my side project I set up and usinf both.

Once again, I admire that you are trying to do a lot, but I think you can help yourself by focussing a bit more on deepening your knowledge as opposed to widening it too much now. I feel that, by now, you should start to get to a stage where you have those SQL queries in your toolbelt. If not, you should first get that down, since they are really fundamental, also for Postgres and other DBs. But also, having to google them is natural and I still need to do that with anything beyond the basics as well.

Also you say Postgres and relational databases are more interesting to you, but it seems to me that MySQL is pretty much the OG relational database.

@RHSebregts I see what i are mean. Just to be sure that I am following you in expected way, should I finish with SQLite or in order to do assignment better I need to re-do it with PostgreSQL? I feel that in this case Postgress is more teaching method.

RHSebregts · 2025-06-07T14:01:27Z

I think that I have two problems in this module. First is a lack of time, we got mysql, next week nosql... I have not mix but the real mash in my head. And the second issue is that I am not able to remember the sql sintax. Evrry time i have to google or ask chat. Maybe because of this I try not to play with different approaches or structures for the databases. PostrgeSQL and relational databases is more interesting for me. However, in my side project I set up and usinf both.

Once again, I admire that you are trying to do a lot, but I think you can help yourself by focussing a bit more on deepening your knowledge as opposed to widening it too much now. I feel that, by now, you should start to get to a stage where you have those SQL queries in your toolbelt. If not, you should first get that down, since they are really fundamental, also for Postgres and other DBs. But also, having to google them is natural and I still need to do that with anything beyond the basics as well.
Also you say Postgres and relational databases are more interesting to you, but it seems to me that MySQL is pretty much the OG relational database.

@RHSebregts I see what i are mean. Just to be sure that I am following you in expected way, should I finish with SQLite or in order to do assignment better I need to re-do it with PostgreSQL? I feel that in this case Postgress is more teaching method.

Let's finish this in MySQL!

RHSebregts · 2025-06-18T10:43:47Z

Week2/Assignment/aggregates.js

    GROUP BY 
      rp.paper_id;
  `);
-  console.log("\n1️⃣ Papers and number of authors:");


Using emojis is completely fine! Sorry for giving you the impression you should've changed that!

aleksandrstarshynov added 3 commits June 4, 2025 13:32

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RHSebregts self-assigned this Jun 4, 2025

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aleksandrstarshynov added 7 commits June 7, 2025 20:16

Update add_mentor_column.js

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Update aggregates.js

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Update create_author_paper_table.js

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Update create_research_papers_table.js

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Update create_research_papers_table.js

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Update insert_sample_data.js

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RHSebregts reviewed Jun 18, 2025

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RHSebregts added Approved and removed Needs work labels Jun 18, 2025

		@@ -0,0 +1,21 @@
		const sqlite3 = require('sqlite3').verbose();

		@@ -0,0 +1,42 @@
		const sqlite3 = require('sqlite3').verbose();

		const db = new sqlite3.Database('example.db');

Oleksandr starshynov w2 databases #20

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Oleksandr starshynov w2 databases #20

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aleksandrstarshynov commented Jun 4, 2025

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aleksandrstarshynov commented Jun 7, 2025

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RHSebregts commented Jun 7, 2025

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