Your queries work. But they are slow. A simple SELECT takes seconds instead of milliseconds. On a table with millions of rows, it could take minutes. The fix is almost always the same: add an index. In the previous article, you learned about window functions. Now you will learn how to make all your queries run fast. What Is an Index? Think of a book’s index at the back. If you want to find “window functions” in a 500-page book, you have two options: ...

GROUP BY is great for summaries. But it collapses your rows. You get one row per group. What if you want the summary and the individual rows at the same time? That is what window functions do. They calculate across rows without removing any of them. In the previous article, you learned about aggregation and subqueries. Window functions are the next level. What Are Window Functions? A window function performs a calculation across a set of rows that are related to the current row. This set of rows is called a window. ...

You know how to get individual rows. But what if you need answers like “How many books did we sell?” or “What is the average book price?” That is where aggregation comes in. In the previous article, you learned how to combine tables with JOINs. Now you will learn how to summarize data across many rows into a single answer. Aggregate Functions Aggregate functions take many rows and return a single value. ...

So far, you have worked with one table at a time. But real databases have many tables, and the interesting answers come from combining them. In the previous article, you learned how to add and modify data. Now you will learn how to pull data from multiple tables at once using JOINs. Why Tables Are Related In our bookstore database, we have separate tables for books and authors. Why not put everything in one table? ...

Every time you see the padlock in your browser, two computers perform a secret handshake. They agree on a secret key — without ever sending that key across the internet. And your browser checks that the server really is who it claims to be. This post explains exactly how that works: HTTPS, the TLS handshake, keys, and certificates. In simple steps. The Problem: Plain HTTP Is Readable HTTP sends everything as plain text. Your password, your messages, your card number — all of it. ...

In the previous article, you learned how to read data with SELECT. But a database is not useful if you cannot add, change, or remove data. This article covers the three commands that modify data: INSERT, UPDATE, and DELETE. You will also learn about transactions — a way to make sure your changes are safe. Our Sample Database We continue with the same online bookstore database. If you need to set it up, copy the CREATE TABLE and INSERT statements from the first article. ...

You have data. You need to get answers from it. SQL is the language that does this. Every app you use — social media, banking, shopping — stores data in a database. SQL is how developers read, filter, and organize that data. It has been around since the 1970s, and it is still the most important skill for working with data. What Is SQL? SQL stands for Structured Query Language. It is a language for talking to databases. You write a query, and the database gives you the answer. ...

In the previous tutorials, we learned how to build images, run containers, use Compose, and manage volumes and networks. Everything so far happened on your local computer. Now it is time to deploy. In this tutorial, you will learn how to move your application from your laptop to a production server. The Deployment Workflow Deploying with Docker follows a simple pattern: Build the image on your computer (or in CI/CD) Push the image to a registry Pull the image on the server Run the container on the server Your Computer Registry Server ┌──────────┐ ┌──────────────┐ ┌──────────┐ │ Build │────►│ Docker Hub │────►│ Pull │ │ Image │push │ or ghcr.io │pull │ & Run │ └──────────┘ └──────────────┘ └──────────┘ Docker Hub — The Default Registry Docker Hub is the default place to store and share images. It is free for public images and offers one private repository on the free plan. ...

In the previous tutorial, we used Docker Compose to run an app with a database. We briefly mentioned volumes and networking. Now let’s understand them properly. These two topics answer two important questions: Volumes: How do I keep data when a container is removed? Networking: How do containers talk to each other? Why Containers Lose Data Containers are designed to be temporary. You can create them, destroy them, and replace them. This is a feature, not a bug — it makes containers predictable and easy to deploy. ...

A lot happened in AI this week. The AI coding tool rankings changed. Two big AI companies filed to go public. And Google released a model that writes text in a new way. Here is everything that matters for developers, in one short read. 1. OpenCode Is the New #1 AI Coding Tool By GitHub stars, OpenCode now leads every open-source AI coding tool. Tool GitHub stars OpenCode 172K Gemini CLI 105K OpenAI Codex CLI 90K Cline 63K Goose 49K Aider 46K But popularity is not the full story. OpenCode has one feature the others do not. ...