Five common SQL mistakes, including SELECT *, missing indexes, poor joins, and NULL traps, with practical fixes for faster, clearer queries.

Callbacks, promises, and async/await all solve the same problem: coordinating work that finishes later. Here's how each works, when to use it, and the mistakes to avoid.

Seven habits that slow JavaScript beginners down — from var and loose equality to ignored async calls and skipping real projects — plus concrete fixes you can apply this week.