Database Indexing Explained: How B-Trees Make SQL Fast

Database indexing explained for beginners, step by step, with no jargon. See how a database index and a B-tree turn a slow full table scan into a 3-read lookup. This applies to MySQL, PostgreSQL, SQL Server and most relational databases. If you've wondered "why is my SQL query slow?" or "how do database indexes work?", this whiteboard explainer is for you. It's also good prep for system design and backend interviews. In this video: • What a database index is (the phone book analogy) • Full table scans and why disk reads are slow • Sorted data, binary search and the problem with plain trees • What a B-tree index is and how a lookup works • Range queries, composite indexes and column order • The hidden cost of indexes, and when the database ignores yours ⏱ CHAPTERS 00:00 Why is this SQL query slow? 00:17 What you'll learn about database indexing 00:30 The phone book problem 00:56 Tables, rows and columns 01:23 What is a full table scan? 01:50 Why disk reads make scans slow 02:16 What is a database index? 02:42 Sorted data and binary search 03:21 The catch with sorted data 03:45 Tree indexes 04:14 What is a B-tree index? 04:52 How a B-tree lookup works 05:20 Index pointers to table rows 05:46 Range queries with indexes 06:14 The cost of indexes 06:42 Composite indexes and column order 07:15 When the database ignores your index 07:51 Recap 08:17 What to learn next 🔔 Subscribe to @saurabhatscale for more system design and database concepts explained visually. 💬 Which concept should I explain next? Tell me in the comments. #DatabaseIndexing #SQL #BTree #SystemDesign #Databases