I started building runtime.school because when I was practicing SQL, everything felt disconnected — learn a concept in one place, solve random questions somewhere else, then use totally different data for projects.

So I tried putting it all together with lessons, practice questions, projects, and the same realistic datasets throughout.

If you have a few minutes, I’d really like to know what feels confusing, repetitive, too easy/hard, or missing. Especially anything that would make learning/practicing SQL better.

Suppose an interviewer asks you something like "find the top three products in each category by sales last quarter." Before you write the query, what would you clarify?

For me, I’d want to know what “sales” means -  units, revenue, or number of orders Then, I'd want to know things like how ties should work, which dates count, and what one row in the output should represent.

I’ve been thinking about how SQL interviews test more than whether you can produce a query. They also give you a chance to show how you frame the problem, explain your choices, and check your work.

So, I put together a guide on what to expect and how to prepare: What to Expect in a SQL Coding Interview

If you’ve recently done a SQL interview, what’s one thing you wish you’d known or asked beforehand?

I know when people are starting out, SQL joins can be a bit confusing so I broke it down in a small vid using Hinge as an example

https://www.instagram.com/reel/Degl_hnoRsz/?mdxt=MTk5dXE2NHZreTR4aw==

Summary of the breakdown is -

• Table A: people you've liked
• Table B: people who've liked you
• Both share one key: person_id

The 4 joins:

• INNER JOIN: only the mutual likes. Someone has to be in both tables to show up.
• LEFT JOIN: everyone you liked. If they didn't like you back, their side comes back as NULL.
• RIGHT JOIN: the mirror image, everyone who liked you, with NULL where you didn't like them. In practice most people just swap the tables and use a LEFT JOIN.
• FULL OUTER JOIN: everyone from both tables, with NULLs on whichever side is missing.

Hope this helps!

If you're working with SQLite and prefer using a graphical interface instead of the command line, I created a tutorial demonstrating data exports using Letos (formerly SQLiteStudio).

The video covers:

• Exporting individual tables to CSV
• Exporting query results
• Generating SQL scripts for an entire database
• Demonstrating the export process step by step using Letos 4.0.3

I also have tutorials covering SQLite's command-line tools, so this provides a GUI-based alternative for those who prefer working with a desktop application.

You can watch the tutorial here: Exporting Data with Letos (Formerly SQLiteStudio) | CSV, SQL & More

I'd be interested to hear how others handle SQLite exports, particularly when deciding between exporting individual tables and generating a complete SQL script.

Java: Covered variables, data types, and literals today.

MySQL: For my Retail Sales Analysis project, I downloaded the dataset and created the database, but I got an error when importing the data into MySQL Workbench. I’m going to debug it tomorrow.

Has anyone hit import errors with Workbench before? I’ll post the exact error message when I’m back on it, but if there are common causes worth checking first (file encoding, date formats, import wizard vs. LOAD DATA), I’d appreciate hearing them.