Database Star

Do you use SELECT * in production code?

I never use it in production queries.

Why?
- It can return more columns than you need.
- The order of columns might change
- It makes queries harder to maintain

Instead, I specify the columns that I actually want.
I do, however, use SELECT * when exploring data or trying to understand what's in a table.

What about you?

1 month ago | [YT] | 48

Database Star

When a query is slow, here’s my usual process:

1. Check the execution plan. Is it using the right index? Is it missing an index that I think can help?
2. Look at the WHERE clause. Is it filtering efficiently?
3. Review Joins. Is it joining more tables than it needs?
4. Reduce the result set early. Can I limit the rows before doing heavy calculations?

Improving performance is rarely about rewriting the whole query. Most of the time you can improve it with one or two tweaks.

How do you usually start troubleshooting?

1 month ago | [YT] | 76

Database Star

Need some inspiration for your next database project?

I’ve put together a free **Database Design Project Guide,** which is a collection of real-world database designs you can use as examples or starting points.

It includes:

- ERDs and table definitions
- Sample SQL for some of the projects
- Designs for eCommerce, flight bookings, AirBNB, train tickets, movie theatre bookings, and more.

Whether you’re learning database design or looking for project ideas for your portfolio, this guide will save you hours.

Get your free copy here: databasestar.mykajabi.com/lpkj-dbdesign/?community…

Which project domain would you design first?

1 month ago | [YT] | 47

Database Star

Here’s a quick SQL puzzle for you.

SELECT department_id, COUNT(*) AS total
FROM employee
GROUP BY department_id
HAVING COUNT(*) > 5;

What do you think this returns?

2 months ago (edited) | [YT] | 39

Database Star

If your SQL query feels painfully slow, here’s one thing you can look at:

Check the columns in your WHERE clause.

If they aren’t indexed, or you’re applying functions to them, the database can’t use the index effectively.

For example:

WHERE YEAR(order_date) = 2025

This forces a scan of the entire table, because if you have an index on order_date, the index can’t be used.

Instead, compare directly to a date range:

WHERE order_date >= '2025-01-01'
AND order_date < '2026-01-01'

You’ll get the same result, but the index should be used, so it would be much faster.

Have you run into this before?

2 months ago | [YT] | 150

Database Star

Got a question for me?
I’m recording a special Q&A video soon, and I’d love to answer your question in it.

If there’s something you’ve always wanted to ask me about my career, my opinions, SQL, databases, performance, career advice, tools, or anything else related, now’s the time.

Submit your question here: docs.google.com/forms/d/e/1FAIpQLScPqOqO9r86UT5waV…

If it’s something you’ve been wondering, chances are others are too.

Looking forward to seeing what you send in!

3 months ago | [YT] | 13

Database Star

Want some database design examples?

I've created a range of "Database Design Guides", based on some of my YouTube videos on database design. They have the ERD from the video (such as a movie database, AirBNB, eCommerce, hotel booking, and many more), the explanations of the tables and columns, and the SQL to create the database.

You can get all of these Database Design guides here: databasestar.mykajabi.com/lpkj-dbdesign?community=…

4 months ago | [YT] | 99

Database Star

Do you struggle to understand complex queries?

Whenever I see a long query, or one with a lot of columns, or lots of joins, or many subqueries, it can seem overwhelming.

My first thought is, what on Earth is this query doing?

But over time, as I saw more and more of these complex queries, they got easier to understand.

There are three things that I do whenever I encounter a complex query to understand what the query is doing and what the results mean.

On Wednesday at 2 PM, I’ll be sending an email that includes:

- what these three things are
- how they help me
- how you can use them for complex queries you find

Enter your email on this page to get the email with all of the details on these techniques:

Here’s the page: www.databasestar.com/value/?utm_source=ytcom&utm_m…

10 months ago | [YT] | 50

Database Star

Only 24 hours to go!

My Black Friday 2024 Course Bundle is available for the next 24 hours only.

It includes my three most popular courses (SQL Simplified, Effective Database Design, Write Faster SQL) and you get a 50% discount from the regular price.

I don’t know when I’ll offer this bundle again…

So if you want to improve your SQL skills and your career, and get better at your job, check out this bundle: databasestar.mykajabi.com/offers/oPBtEzjc

10 months ago (edited) | [YT] | 6

Database Star

You know that special deal I mentioned a couple of days ago?

Well, here it is.

My Black Friday 2024 Course Bundle: databasestar.mykajabi.com/offers/oPBtEzjc

I’ve bundled three of my most popular courses together:

- SQL Simplified: learn the fundamentals of SQL
- Effective Database Design: learn how to design an effective and robust database and create it with SQL
- Write Faster SQL: learn how to improve the performance of your SQL queries

All courses are shown in the four vendors I teach (Oracle, SQL Server, MySQL, and Postgres), come with a 30-day money back guarantee, include PDF versions of the course and other bonuses.

You can get this bundle for 50% off the full price of the courses.

This is the largest discount I’ve ever done.

However… it’s only available for the next 48 hours.

Find out more here: databasestar.mykajabi.com/offers/oPBtEzjc

10 months ago | [YT] | 9