#testing techniques

Imagine your database is a huge school library. Tables = shelves Rows = books Queries = asking the librarian for a book Now here’s the problem If the librarian checks every single book, it’s slow But if the librarian uses a catalog (index) → FAST! That’s exactly what indexes do in databases like MySQL. What Is an Index? Index = Book’s Table of Contents Instead of reading the whole…

Imagine a huge library with millions of books.If the books are not organized, finding one book will take forever. Now imagine the library has a magic index card system that tells you exactly where each book is.That magic system is called an INDEX in databases. In this lesson, we’ll learn about Creating and Managing Indexes inMySQL— step by step, slowly, clearly, and with lots of examples. What…

Imagine you have a huge storybook with 10,000 pages. If I ask you to find page 7,432,would you start reading from page 1? Or would you use the index at the back of the book? Databases work the same way.That magical shortcut is called an INDEX. What Is an Index? An index is like: A book index A phone contact list A table of contents It helps MySQL find data faster without checking every…

Imagine your database is a school Students = Rows Register = Table Rules = Constraints If there are no rules, students can: Skip their name Write age as -5 Enter marks as 9999 That would be chaosSo we use constraints to keep data clean, safe, and sensible. Today, we learn two important rules: DEFAULT Constraint – “If you forget, I’ll fill it for you.” CHECK Constraint – “I will only…

Unique and NOT NULL Constraints Imagine you are making a school register. Every student must have a roll number → it cannot be empty No two students can share the same roll number That’s exactly what NOT NULL and UNIQUE constraints do in a database We’ll learn this using MySQL. What Are Constraints? (Super Simple) Constraints are rules that tell the database: “Hey! Data must behave…

What Are Keys in a Database? A key is like an ID card for data. It helps identify records It helps connect tables It keeps data clean and organized We mainly use two keys: Primary Key Foreign Key Primary Key (The Super ID) Imagine your school roll number: No two students have the same roll number Everyone must have one It never changes That’s exactly what a Primary Key does! Rules…