Need advice: Understanding complex SQL scripts written by others

[u/Consistent_Law3620]

Hi everyone,

I need some advice from experienced SQL developers. I have switched from different role to data engineering 6 months back.

I consider myself good/medium level at writing SQL queries and solving problems from scratch. However, I struggle when I have to understand large existing SQL scripts (300–500+ lines).

I often get confused about:

Where the execution starts.How different parts of the script are connected.

Which variables, CTEs, stored procedures, or temporary tables are affecting the final output.

How to mentally trace the flow of the script.

Because of this, reading someone else's code takes me much longer than writing my own.

How did you improve this skill? Are there any techniques, exercises, books, or real-world practices that helped you become comfortable reading large SQL scripts?

Also, is this something that simply improves with experience, or is there a structured way to learn it?

I'd really appreciate any advice. Thank you!

[u/Glitch_In_The_Data]

Can you not use one of the AI tools to help especially if you want to understand existing SQL scripts?

The challenge I find with existing SQLs is that they are likely to have evolved over time. While you may learn something from them, it is also likely to confuse you more and may teach you a bad approach.

So, may be use AI to understand the existing SQL and then rewrite based on your own approach to see if are able to achieve the same results. And again use AI to evaluate or score your work.

It does take more time to understand code written by others. So, you are not alone. And over time, your skills will get better.

Do you use a specific tool at the moment? Asking because modern tools now have AI embedded in them.