Part 3: Introduction to SQL – Learn the Language of Databases
📍 Introduction
Databases store data — but how do we talk to them? That’s where SQL (Structured Query Language) comes in. SQL is the language we use to interact with relational databases: we ask questions, make changes, and organize information — all using SQL commands.
Whether you want to retrieve customer data from an online store or insert marks into a student database, SQL is your go-to tool.
🔹 What is SQL?
SQL (Structured Query Language) is a programming language used to create, read, update, and delete data in a relational database. These four actions are commonly referred to as CRUD operations.
SQL works across many relational databases like MySQL, PostgreSQL, SQLite, Oracle, and SQL Server.
🧠 Think of SQL as a Conversation
Imagine a database is like a library.
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If you want to find a book, you say: "Show me all the books by J.K. Rowling."
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If you want to add a book, you say: "Add this new book to the shelf."
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If you want to update a book’s details, you give new information.
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If you want to remove a book, you say: "Take this book off the shelf."
SQL is how we say those things to a database — in a structured, computer-friendly way.
🛠️ Basic SQL Commands (With Examples)
Let’s explore the most common SQL commands using a Students table example:
📌 1. SELECT – Read Data
SELECT * FROM Students;
Retrieves all records from the Students table.
SELECT Name, Marks FROM Students WHERE Marks > 80;
Shows names and marks of students who scored above 80.
📌 2. INSERT – Add Data
INSERT INTO Students (Name, Course, Marks)
VALUES ('Nina', 'Science', 88);
Adds a new student named Nina with a Science course and 88 marks.
📌 3. UPDATE – Modify Data
UPDATE Students
SET Marks = 95
WHERE Name = 'Ravi';
Updates Ravi’s marks to 95.
📌 4. DELETE – Remove Data
DELETE FROM Students WHERE Name = 'Sara';
Deletes the record for Sara.
📋 Example Table for Context
| StudentID | Name | Course | Marks |
|-----------|-------|------------|-------|
| 1 | Aisha | Math | 85 |
| 2 | Ravi | Science | 90 |
| 3 | Sara | English | 78 |
These SQL commands let you manage data in this table easily and efficiently.
💡 Pro Tip: Case Sensitivity
SQL keywords (like SELECT, FROM, WHERE) are not case-sensitive, but it's good practice to write them in uppercase for readability.
Recap
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SQL is the language used to interact with relational databases.
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The four key operations are:
SELECT,INSERT,UPDATE, andDELETE. -
You can retrieve, add, edit, and remove data using easy-to-understand commands.
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SQL works across most relational databases like MySQL, PostgreSQL, and SQLite.
✅ What’s Next?
In Part 4, we’ll explore Keys and Relationships — the magic behind how multiple tables in a database talk to each other. You’ll learn about Primary Keys, Foreign Keys, and how to build logical connections in your data.