The BI School

12/05/2026

I think that sometimes I'm trying to make up for my lost career years by helping others get started in their own careers.

That's why I teach SQL to career starters or mover-uppers looking for a promotion or simply hoping to be more effective in their current role.

And it doesn't have to cost a lot either.

I'm in the process of building a Skool training course to help get people started with SQL.

You can access it here: https://www.skool.com/learn-sql-for-free-9250

11/05/2026

I was given a task once to "See if I could do something with this very slow SQL query."

It was indeed very very slow - took over 36 hours to run as a background process.

The customer wanted to see if it could be sped up, and the task was passed to me.

The query contained CTEs. Lots of them. Maybe 30 or 40 from memory.

And although it wasn't handling huge amounts of data - we're talking 200k -300k - the CTEs were killing it.

Because CTEs are 'heaps' - that is, they are unindexed datasets.

This was in SQL Server, so I converted all the CTEs to temp tables. I gave each table a primary key - a clustered index, and applied some other indexes where needed.

Whilst at it, I tweaked some of the calculations, tidied the whole thing up, and fixed some other minor issues.

The new version of the query - the one that had temp tables instead of CTEs....

It ran in eleven seconds.

From 36 hours - to 11 seconds, all because of this small piece of work.

Knowing that this was what was required was down to experience, but this is the sort of thing we talk about at The BI School - real world examples and applications of the stuff you're learning.

This piece of work turned me into a rock star - at least within the context of that organisation and specifically with that one very happy customer.

Want to learn SQL?

Want to learn how to use SQL to give your career a rocket up the arse?

Visit www.thebischool.com today, and let's get you on your way.

10/05/2026

Window functions in SQL are an amazing addition to your arsenal.

Here are my top choices:

DENSE_RANK - this returns a ranking based on whatever criteria you set out, and partitioned however you choose too. I would use this to find the current and previous role that an employee has, or the top three highest earners by department for example. Very useful.

ROW_NUMBER - Simply returns a unique incremental value, one for each row in a dataset. Again these can be partitioned so you can reset the numbering when some other value changes such as region or product.

LAG/LEAD - these little gems have been two of the biggest game-changers ever in SQL. By referencing the next or previous row in a dataset, you can avoid multiple self joins or additional calculations. Has helped me reduce the size of some queries by around 80%.

SQL Window functions are very important to know.

If you'd like any further information on this or any other area of SQL, go to https://thebischool.com/courses/sql-superhero-program/

09/05/2026

Going for a promotion?

Lack of SQL skills blocking you?

It's a familiar tale.

Opportunities like this don't come round very often and typically, there's someone with more technical experience in the running.

Maybe it's one of your current colleagues - maybe it's an external candidate.

Doesn't matter.

The onus is on you to skill up - and fast.

So what are you going to do?

Visit www.thebischool.com and I'll help you.

08/05/2026

The three key skills for a career in data are:
1. Excel
2. A data vis tool e.g. Power BI, Tableau, Looker etc.
3. SQL

Nail these and you're well on your way.

Excel is the foundational skill for working with data. It's not just about presenting data in tables and charts, it's also about ninja skills with formulae such as lookups and complex calculations.

Working with data visualisation tools is where you get noticed. Again, there's more to it than simply using charts and graphs, even when they're all fancy and interactive. There's the query editor, DAX and understanding the underlying data model.

As for SQL - well that's where you place yourself high above all the other candidates for roles because, let's face it, EVERYONE has Excel and a data vis tool, so how do you stand out?

SQL.

If you're already learning SQL, this might help. It's a Cheat-Sheet covering the basic commands, syntax and query structure.

https://thebischool.com/cheats-postgresql/

It's proving quite popular, so grab a copy now.

This guide will help you remember those key commands, functions and syntax when working in PostgreSql

07/05/2026

FREE - SQL Cheat Sheet - PostgreSql

Help yourself to your own free SQL cheat-sheet, written for PostgreSql.

Print it out and keep it by your desk, or open it in a web browser and save it as a favourite.

Here it is...

This guide will help you remember those key commands, functions and syntax when working in PostgreSql

16/08/2025

I've spent much of 2025 job-seeking.

I've changed my job loads of times over the years, but this year it feels... different.

It's harder, less personal, more competitive, colder...

There's zero room for complacency.

And over the last few months, I've been jotting down my thoughts. Making lists of tips, tricks and hints for other jobseekers. Things that have worked for me, and things that have failed.

Here are a few from the top of my list - and it's in no particular order.

• Believe in yourself, know your worth and be certain about your goals. Don't allow a recruiter to dictate your directions, values or financial worth. Listen to their advice, obviously, but know your self.

• Plan ahead. Be organised. Log all applications in a spreadsheet, and make sure it gets updated. Daily. Organise emails, job descriptions/specs, notes into folders. Delete the stuff that falls out of relevance.

• Be positive - even if you've been looking for ages and you're feeling the pressure. Nothing is more off-putting than desperation or bitterness. I've spoken to skilled, experienced people who've been out of work for months and I wouldn't hire them - based solely on how angry they are, and how unfair they seem to feel life has treated them.

• Give it time - the MINIMUM time from application to offer is probably around six weeks, and that's without people being on holiday. Be patient.

• Put in the effort - nothing comes easy. If you want it, work for it. Read the job specs, know the company, prepare properly for interviews, do some additional training and certifications if necessary.

That's just a snippet of what's to come.

Over time, I'll properly write these up and present them, probably in a downloadable document.

But for now, keep plugging away.

And good luck out there. It's tough.

15/08/2025

Do you understand why this WHERE clause returns NO RESULTS?

29/07/2025

For the next couple of days, I'm offering access to my SQL Superhero Program for half price for the first four months.

That's £29.50 for months 1-4, then back up to £59 from month 5.

Most people complete the learning in four months, so hopefully you'll not hit month 5.

This offer expires at midnight on Thursday.

13/06/2025

I wrote this book in 2025 to help people learn SQL.

I can't believe the response I've had.

Anyway, it's currently on sale for £5, but atvthis rate i'll be putting the price up very soon.

https://payhip.com/b/YD4J5

Get your copy quickly.

Ten Simple Steps to Master SQL is your complete guide to getting started with SQL.If you're an aspiring data analyst, data engineer, business intelligence analyst or developer or want to work in any capacity with data, then you're going to need a str...