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What is a Database?

A database is an organized collection of structured data stored electronically. Think of it like a very powerful spreadsheet. Databases are used everywhere: websites store user accounts, banks store transactions, hospitals store patient records. SQL (Structured Query Language) is the standard language used to create, read, update, and delete data in a database.

Key Database Concepts

Table — Like a spreadsheet with rows and columns

Row (Record) — One entry in a table (e.g., one user)

Column (Field) — A category of data (e.g., name, age, email)

Primary Key — A unique ID for each row (e.g., user_id)

SQL — The language used to query and manage databases

RDBMS — Relational Database Management System (MySQL, PostgreSQL, SQLite)

A Simple Database Table

Example

-- This is what a database table looks like:
-- Table: students

-- | id | name    | age | city      |
-- |----|---------|-----|-----------|
-- |  1 | Alice   |  20 | Mumbai    |
-- |  2 | Bob     |  22 | Delhi     |
-- |  3 | Charlie |  19 | Bangalore |
-- |  4 | Diana   |  21 | Mumbai    |

-- SQL to get all students:
SELECT * FROM students;

-- SQL to get just names:
SELECT name FROM students;

Try It Yourself: SQL Concepts in Action

Try It Yourself: SQL Concepts in ActionJavaScript

JavaScript Editor

✓ ValidTab = 2 spaces

// SQL runs on a database server, but here we simulate it in JavaScript
// to show you how SELECT queries work conceptually

// This is our "database table" — students
const students = [
  { id: 1, name: "Alice",   age: 20, city: "Mumbai"    },
  { id: 2, name: "Bob",     age: 22, city: "Delhi"     },
  { id: 3, name: "Charlie", age: 19, city: "Bangalore" },
  { id: 4, name: "Diana",   age: 21, city: "Mumbai"    },
];

// SELECT * FROM students  (get all rows)
console.log("=== All Students ===");
students.forEach(s => console.log(s.id + " | " + s.name + " | " + s.age + " | " + s.city));

// SELECT name FROM students  (get just names)
console.log("\n=== Names Only ===");
students.forEach(s => console.log(s.name));

// SELECT * FROM students WHERE city = 'Mumbai'
console.log("\n=== Students from Mumbai ===");
students.filter(s => s.city === "Mumbai")
        .forEach(s => console.log(s.name));

Result

Click ▶ Run to see the result

Edit the code on the left, then click Run

JavaScript|23 lines|904 chars|✓ Valid syntax

UTF-8

What is a Database?

What is a Database?

Key Database Concepts

A Simple Database Table

Try It Yourself: SQL Concepts in Action

Quick Quiz