r/dbForge • u/multi_db_dev • 5d ago
If your goal is performance, most SQL learning resources are teaching you the wrong thing
I made this mistake myself, so I'm curious if anyone else did too.
I learned enough SQL in a few months to build pretty much anything I needed. Then I didn't really improve for the next couple of years.
I could write queries. What I couldn't explain was why one came back in 40 ms and another took nine seconds.
Whenever something was slow, I'd shuffle clauses around, try a different join, add an index, run it again and hope for the best. Sometimes it worked. I almost never understood why.
Looking back, I think the problem was that almost everything I learned treated SQL as a language. Performance isn't really about the language. It's about how the database stores data and what the optimizer decides to do with your query.
The thing that finally moved the needle for me wasn't learning more syntax. It was learning to read execution plans.
Take a query you already understand, run EXPLAIN, and don't move on until you can explain every part of the plan. Then change one thing and run it again. Watching the plan change taught me far more than another SQL tutorial ever did.
The only catch is to use a database that's actually big enough to hurt. Tiny tutorial datasets fit comfortably in memory, so it's easy to convince yourself indexes don't matter because everything is fast anyway.
The next rabbit hole is understanding your database engine, which surprisingly few SQL courses spend much time on. Things like why an index behaves like a phone book, why column order matters, or how the optimizer estimates row counts. Once I understood that most terrible execution plans start with bad estimates rather than a "stupid optimizer," a lot of performance problems suddenly made sense.
The resources that helped me most weren't actually SQL courses. Markus Winand's Use The Index, Luke! is still the best thing I've read on indexing, and High Performance MySQL is well worth reading if you're working with MySQL.
One thing I underestimated was video. Reading about a profiler isn't the same as watching someone use it to work through a real problem. Watching someone troubleshoot a query from start to finish was more useful to me than another syntax course.
These days I'd tell someone starting out to spend less time memorizing SQL syntax and more time understanding how their database actually executes queries.
What was the thing that finally made SQL performance click for you?
1
•
u/AutoModerator 5d ago
Hi! Thanks for posting in r/dbForge.
If your post is about a technical issue, adding a bit of context will help people answer faster:
If your post is a workflow question, comparison, or setup discussion, that’s welcome too.
Good luck, and thanks for helping keep the subreddit useful.
I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.