SQL Joins Explained with Simple Examples
INNER, LEFT, RIGHT and FULL joins, the anti-join trick for "find rows with no match", and why joins sometimes multiply your rows. Clear examples you can run against any SQL database.
Read →
Tips & writing
Notes from the workbench
Practical engineering tips, design theory and performance breakdowns — written for developers and founders who like their advice tested in production.
Filtering by tag #mysql — clear
Why LOWER() and TRIM() Kill Your SQL Index Performance
A query that runs in 4ms locally but takes 9 seconds in production usually has the same cause: a function like LOWER() or TRIM() wrapped around an indexed column. Learn why this makes queries non-sargable, how to spot it in your execution plan, and five engine-specific fixes — from functional indexes to PostgreSQL's citext type.
Read →
Localhost vs 127.0.0.1 in .env: The Bug That Only Appears on Windows
Same code. Same .env. Works on my Linux box, dies on the Windows server with ECONNREFUSED ::1:3306. Here's what localhost actually does under the hood, why 127.0.0.1 is not always the same thing, and the rules I now follow in every .env file.
Read →
Database Indexing Explained for Application Developers
One missing index can turn a 5ms query into a 5 second one. What indexes are, how to read EXPLAIN, how composite indexes really work, and when an index makes things worse.
Read →