Learn how to build a custom Typora theme from scratch with this beginner-friendly guide. Customize colors, fonts, and layouts to create your perfect writing environment.

How to Create a Custom Typora Theme (Step-by-Step Tutorial)

Learn SQL joins from scratch with real customer and order examples. This beginner-friendly guide covers INNER, LEFT, RIGHT joins and how to combine data from multiple tables with practical queries you can try today.

SQL Joins Explained: A Beginner's Guide with Real Customer Data Examples

My 3-week journey from SQL beginner to writing 4-table joins. A step-by-step learning path with 50 practice exercises that took me from zero to confidently querying multiple tables.

From Zero to Joining 4 Tables: My SQL Learning Path (With Practice Exercises)

I spent 3 weeks learning SQL joins so you don't have to. A beginner-friendly guide to INNER JOIN and LEFT JOIN with real examples, common mistakes, and practice exercises.

I Spent 3 Weeks Learning SQL Joins — Here's the Only Tutorial Beginners Actually Need

Learn three SQL aggregation patterns that solve real business problems: time-series analysis for revenue trends, customer segmentation for VIP identification, and cross-category matrices for regional performance. These career-focused queries will make you indispensable at work.

3 SQL Aggregation Patterns That Will Make Your Boss Think You're a Data Wizard

Learn SQL aggregation by building a real sales dashboard. Step-by-step tutorial with COUNT, SUM, AVG, GROUP BY, and HAVING. Perfect for data analyst portfolios.

Build Your First Sales Dashboard: SQL Aggregation for Beginners

Learn the critical difference between WHERE and HAVING in SQL. Discover why your aggregate queries fail and the simple fix that will save you hours of debugging.

WHERE vs HAVING: The SQL Mistake That Breaks Your Queries

Learn the 5 most common SQL GROUP BY mistakes beginners make and how to fix them. Understand WHERE vs HAVING, COUNT() variations, NULL handling, and execution order.

5 SQL GROUP BY Mistakes That Make You Look Like a Beginner (And How to Fix Them)

SQL's AVG() function excludes NULL values by design—causing beginners to get technically correct results but wrong business insights. Learn how AVG() handles NULLs, three practical solutions (COALESCE, WHERE, CASE), and a decision framework to choose the right approach for your analytics.

SQL Averages Are Lying to You: The NULL Problem Nobody Talks About

COUNT(*), COUNT(column), and COUNT(DISTINCT) all give different results. Learn which SQL COUNT function to use in every situation with real examples.

Stop Counting Wrong: The 3 Types of COUNT() Every SQL Beginner Needs to Know

Learn 6 essential VS Code keyboard shortcuts that replace 90% of mouse clicks. Boost your coding productivity instantly with this beginner-friendly guide to keyboard navigation.

How to Navigate VS Code Without Ever Touching Your Mouse (Beginner's Guide)

Stop struggling with VS Code defaults. Change these 7 essential settings before coding. Auto-save, formatting, and more. Beginner-friendly setup guide.

7 VS Code Settings Every Beginner Should Change (Before Writing Your First Line of Code)

Learn how to set up free Cloudflare R2 image hosting in 15 minutes. 10GB storage, unlimited bandwidth, global CDN. No coding required. Step-by-step guide.

The Complete Beginner's Guide to Cloudflare R2 Image Hosting (2025)

Learn the 5 critical Homebrew mistakes that waste hours of troubleshooting time. Covers PATH issues on Apple Silicon, sudo permission errors, brew doctor warnings, formulae vs casks confusion, and skipping caveats. Includes practical fixes and a quick diagnostic checklist for beginners.

What I Wish I Knew About Homebrew Before Wasting 2 Hours Troubleshooting

This draft outlines a blog post structure, emphasizing engaging introductions, main sections, and clear conclusions with actionable takeaways.

Why Your Mac Software Installation is Broken (And How to Fix It in 10 Minutes)

Learn how to use Homebrew to install any Mac software with a single command, update everything at once, and never manually download .dmg files again. Perfect for beginners who want to save hours on software management.

How I Stopped Manually Installing Software on Mac (And You Should Too)

Master SQL WHERE clause filtering with this comprehensive guide. Learn essential operators, logical conditions, and common mistakes to avoid.

SQL WHERE Clause Explained: Filter Data Like a Pro in 10 Minutes

Learn the 7 common SQL mistakes beginners make and how to fix them for cleaner, more efficient queries.

7 SQL Mistakes Every Beginner Makes (And How to Fix Them)

Learn how to optimize your note-taking with Markdown, enhancing productivity for students and developers alike.

How to Take Better Notes with Markdown (Student & Developer Edition)

Markdown simplifies writing for developers, ensuring universal compatibility, focus on content, and seamless integration across various platforms and tools.

Why Developers Love Markdown (And 5 Reasons Developers Love Markdown)

Learn Markdown with this essential cheat sheet for beginners, covering syntax rules, common mistakes, and practical examples for everyday writing.

Markdown Cheat Sheet for Absolute Beginners (Bookmark This!)

Easydict is a powerful macOS translation tool that aggregates multiple sources, enhancing productivity for multilingual work and language learning.

Easydict: The Ultimate macOS Translation Tool for Multilingual Work

Apple Notes has evolved into a powerful, free note-taking app with features like AI tools, collaboration, and privacy, making it highly effective.

Apple Notes: The Underrated Powerhouse You Already Own

This guide covers image hosting for Markdown, detailing solutions, benefits, and effective strategies to enhance your content sharing.

Image Hosting for Markdown: The Complete Guide to Picture Beds

Daily English learning emphasizes consistency over intensity, using sustainable habits and practical tools for steady progress.

Learning English Day by Day

language

programming

tools

writing

pre-dev

Search

This document is a published menu titled "Search," created on July 2, 2021, featuring a search icon.

History

About

This document provides information about the "About" menu, which is published and includes details such as the date and icon.

Master database relationships with practical examples using customers and orders

Database

Typora CSS customization and Markdown editor theme

Writing

A step-by-step 3-week roadmap with 50 practice exercises to master multi-table SQL queries

Master INNER JOIN and LEFT JOIN with real examples. No fluff, just the SQL knowledge beginners actually need.

Master three aggregation patterns that answer executive questions and fast-track your data career

A portfolio-ready project that teaches SQL aggregation through building 5 real business reports

author

image_url

publish_date

read_time

password

icon

date

Medium Tages

type

slug

status

Medium Subtitle

title

summary

Table

Post Board

Config

Welcome to Leon's Blog featuring technical tutorials, Notion templates, learning resources, and more. Happy reading!

programming

📝SQL Joins Explained: A Beginner's Guide with Real Customer Data Examples

📝From Zero to Joining 4 Tables: My SQL Learning Path (With Practice Exercises)

📝I Spent 3 Weeks Learning SQL Joins — Here's the Only Tutorial Beginners Actually Need

📝3 SQL Aggregation Patterns That Will Make Your Boss Think You're a Data Wizard

📝Build Your First Sales Dashboard: SQL Aggregation for Beginners

📝WHERE vs HAVING: The SQL Mistake That Breaks Your Queries

📝5 SQL GROUP BY Mistakes That Make You Look Like a Beginner (And How to Fix Them)

📝SQL Averages Are Lying to You: The NULL Problem Nobody Talks About

📝Stop Counting Wrong: The 3 Types of COUNT() Every SQL Beginner Needs to Know

📝SQL WHERE Clause Explained: Filter Data Like a Pro in 10 Minutes

📝7 SQL Mistakes Every Beginner Makes (And How to Fix Them)