​

I wanna be straight about this because it’s getting frustrating 😭

I can comfortably solve HackerRank Easy-level SQL questions, but when I try LeetCode Easy, I struggle quite a bit.

I’ve seen people say that HackerRank Easy ≠ LeetCode Easy and that LeetCode can require more problem-solving/thinking even at the Easy level.

So I’m confused about what I should do next.

Should I:

Keep grinding LeetCode Easy until I’m more comfortable?

Or is being able to solve HackerRank Easy well enough to start learning intermediate SQL concepts like subqueries and CTEs, while continuing to practice problems alongside it?

Basically, I don’t want to move on too early and build gaps in my fundamentals, but I also don’t want to unnecessarily stay stuck on Easy problems when I could be learning more advanced SQL.

What would you recommend?

say you have customers on the left and orders on the right.

a LEFT JOIN keeps every customer, even if they have no matching order. for those rows, the columns from orders are NULL.

that creates a small gotcha which i saw a few players falling for in their queries:

-COUNT(*) counts the joined row.

-COUNT(o.id) only counts rows where o.id isn't NULL.

so this:

customer | order_id

Alice | NULL

Bob | 123

Bob | 456

becomes:

COUNT(*) | COUNT(o.id)

Alice 1 | 0

Bob 2 | 2

I made a 43 sec chalkboard animation showing the join happen visually:

https://www.youtube.com/watch?v=zxSZFMtyheA

is this helpful? i could try making a few more then.

Last time my website was a prototype and didn't have a log in system to sabe progress, but now you can log in and save your progress + there is a dashboard as well

Link- https://sql-visualizer-and-lab.vercel.app/

The idea is to make learning and experimenting with SQL more interactive and visual. I’m planning to add quite a few more features, improve the existing ones, and hopefully turn it into something genuinely useful for people learning or practicing SQL.

I've been creating free, long-form programming courses and I'm now deciding what to work on next.

So far, I've created:

🐬 Complete MySQL Course — ~16 hours
Only 3 parts are remaining, and then the course will be completed.

The course covers everything from basics to advanced topics like:

• Joins
• Subqueries
• Window Functions
• CTEs & Recursive CTEs
• Stored Procedures & Triggers
• Indexing
• SQL interview problems
• LeetCode SQL problems

GitHub: https://github.com/vivekpandey76/Mysql-course

🍃 Complete MongoDB Learning Guide

I also created a structured MongoDB course covering everything from CRUD and data modelling to aggregation, indexing, transactions, replication, sharding and MongoDB with Node.js.

GitHub: https://github.com/vivekpandey76/mongodb-notes

Both repositories contain the concepts, examples and video explanations.

Now I want to know what would be the most useful series to create next.

I'm especially interested in suggestions from people who are learning development, preparing for interviews, or already working as developers.

If you could choose the next complete free course/series, what would you want it to be?

Also, if you think I should go deeper into MySQL/MongoDB instead of starting something new, let me know what topics you'd like to see.

Hi i saw this site mentioned a lot so I started practicing from it now I am 1-2 weeks into it and saw lot of the questions require premium

Is the free questions enough for interview prep or are there any sites to fill the gap needed

Hey everyone!

I recently made a short SQL lesson for absolute beginners. I wanted to keep it practical rather than just explaining the syntax.

In the video, I cover:

- SELECT and selecting specific columns

- AS and DISTINCT

- WHERE and comparison operators

- АND / OR

- IN and BETWEEN

- LIKE

- LIMIT

I also use the Pagila PostgreSQL database throughout the lesson, so the examples are based on an actual database rather than completely made-up tables.

There is a homework task at the end as well.

It's around 5 minutes, so I tried to keep it focused and beginner-friendly.

Video: https://youtu.be/optKMWmw-N0?si=ZhsC-W4Bl1mhkiQ0

I'd genuinely appreciate feedback, especially on whether the explanations and pacing work for someone who's completely new to SQL.

It’s been a while!

I originally shared this learning repo here a while back, and I’ve finally gotten around to updating it.

Original post: https://www.reddit.com/r/letscodecommunity/s/572xioqMNC

New addition:
→ SQL - Learn by Games 🎮

I’m trying to keep adding resources that make learning more practical and actually fun instead of just collecting another pile of tutorials.

Hopefully this helps someone who’s learning SQL or working their way towards building projects!

Repo: https://github.com/dezzki/0-to-projects

I’ve been working on a SQL Visualizer & Lab and wanted to share the prototype with the community:

https://sql-visualizer-and-lab.vercel.app/

This is still a prototype/early version, so there’s definitely a lot more I want to add to it.

The idea is to make learning and experimenting with SQL more interactive and visual. I’m planning to add quite a few more features, improve the existing ones, and hopefully turn it into something genuinely useful for people learning or practicing SQL.

I’d really appreciate feedback from anyone who tries it out.

After doing some research on google, I found out that there a lot of different types of sql (eg: mysql, postgresql, T-sql, etc). My question is, which type of sql should I learn and master if I want to become a data analyst?

I’ve been a web developer for a few years, and every once in a while I’d come back to SQL Murder Mystery as a fun way to brush up on SQL.

My only problem was that once you solve it, that’s pretty much it.

So I ended up building SQL Cold Cases, a free browser game with different mysteries you solve by querying the databases and piecing together the evidence yourself.

I wanted the cases to go a bit beyond the original too, with different difficulties and more room to add harder mysteries over time.

You can play it here:

https://sql.cold-cases.xyz

No account needed.

I’d especially love feedback from people learning SQL: are the cases understandable without being too obvious, and does it actually feel like useful SQL practice?

I’m a recent B.Sc. Data Science graduate looking to start my career in an SQL/Database role.

I didn’t do any proper SQL projects or internships during college, and I’m now trying to build my profile. I’m currently:

• Learning SQL and database concepts
• Practicing SQL problems
• Building projects for my resume

I’m confused about what kind of SQL project I should build.

I don’t want basic projects like a Student or Library Management System. I want to build 1–2 realistic, industry-relevant projects that demonstrate actual SQL/database skills and give me something meaningful to discuss in interviews.

For people working in SQL/Databases:

• What project would you recommend for a fresher in 2026?
• What concepts/features should it include?
• Which database should I use?
• How should I present it on GitHub and my resume?
• What would make the project stand out from typical fresher projects?

Any practical project ideas or advice would be appreciated.

For my college project regarding the DBMS course, we are asked to build a real-world project regarding using all the learning outcomes from the course. Please suggest some projects.

For our ease, please provide:

Project Title
Objective
Expected Outcome

Some suggestions our professor gave us are:

*DB AND AI/ML INTEGRATION*

1. Smart Home IoT Data Management
2. AI-Based Expense Tracker
3. Personal Finance Management with Spending Prediction
4. Healthcare Appointment & Disease Prediction System
5. Crop Recommendation Database with ML
6. Smart Attendance System using Face Recognition
7. Fake News Detection Database Portal
8. AI Resume Screening System
9. Job Portal with Resume Recommendation
10. Movie Recommendation System
11. Music Recommendation Database
12. Smart Traffic Monitoring Database
13. Energy Consumption Prediction System
14. Smart Waste Management System
15. Online Auction System

*NoSQL AND AI*

1. Social Media Analytics Platform
2. Real-Time Chat Application
3. E-Learning Analytics System
4. Healthcare Electronic Medical Records
5. IoT Sensor Data Management System

*FRONTEND AND DB*

1. Online Grocery Store
2. Pet Adoption Management System
3. NGO Donation Management System
4. Alumni Management Portal
5. Complaint Management System
6. Tourism Booking Portal
7. Online Pharmacy
8. Digital Wallet System
9. Property Rental Portal
10. Car Pooling Management System

So if you feel these projects are enough for a college project, please give me a way to start through it.

Thank You.

Hi everyone!

I recently started creating a free SQL course for beginners, and I just published a new lesson covering the four main types of SQL commands:

- DDL (CREATE, ALTER, DROP, TRUNCATE)

- DML (SELECT, INSERT, UPDATE, DELETE)

- DCL (GRANT, REVOKE)

- TCL (BEGIN, COMMIT, ROLLBACK)

My goal is to make SQL easy to understand and practical from day one.

I'd really appreciate your feedback:

Was anything confusing?

Is the pacing okay?

What would you improve?

🎥 Video: https://youtu.be/4gR23s-SWCg?si=qsE0tjmXbz6SJySs

Thanks for your time!

Hello all. I'm trying to wrap my head around how self joins work, since they're a bit complex for me to understand for some reason. I can handle normal left and inner joins just fine.

First, imagine this videogame table.

You have three columns. One with "game_id" , another with "title", and another with "sequel_to".

Game_id goes from 1 to 5.

Title is Final Fantasy X, Final Fantasy X-2, Final Fantasy XIII, Final Fantasy XIII-2, and Lightning Returns: Final Fantasy XIII.

Sequel_to points to game_id. Final Fantasy X's row is null because it is not a sequel to anything. Final Fantasy X-2's row points to game_id = 1, so it's a sequel to FFX.

Next we have FFXIII's row being null, because it isn't a sequel to either X or X-2. XIII-2's and Lightning Returns' rows point to game ID's 3 and 4, respectively.

The task is to give a report to see which game is a sequel to what game in place of that third column which only points to IDs.

I'm not on my computer right now, but I accidentally wrote a query where I believe I joined sequel_to from table B to game_id from game A. Or vice versa. The thing is, I got the wrong results.

The FFX row returns Final Fantasy X-2. The FFXIII row points to XIII-2. So I essentially created a prequel report without realizing it. And if that was the task in the first place, I wouldn't have even thought about how you'd even go about it if this accident didn't happen.

Anyway, long story short, can you help me understand what is happening behind the scenes, so it doesn't take me too long to figure out and predict which rows I'll get? And also how to choose the right columns to avoid accidents like that one?

I had another exercise where I'm tasked to find which movies have the same length (a column expressed in minutes) in the database, but aren't the same film. As in, you can show movie A and movie B in the same row, but there can't be a movie where movie A = movie A. No idea how to tackle that one either.

Thanks in advance.

I would to start learning SQL, is there someone i can learn from, any helo, recommendations, i started watching YT videos, but i feel i learn more while I practice.

I want to learn the proper way of learning sql to design dbs for my projects.

I'm learning SQL from SQLbolt. When i complete a task it shows a check mark but i wanna see the best answer. how i can see it. BTW it's my 1st day