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Grouping Data with GROUP BY

Introduction: What’s the Big Deal About Groups? Start with a relatable analogy. Imagine having a big box of toys: cars, dolls, and building blocks. If you want to know how many of each type of toy you have, what do you do? You group them together! Explain that databases are like giant boxes of information, and sometimes we need to group similar information together to understand it…

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Aggregate Functions

Imagine you’re a detective, and you have a big box of clues (that’s your MySQL database!). Sometimes, you don’t need to look at every single clue in detail. Instead, you want to get a quick summary, like “How many clues do I have in total?” or “What’s the most important clue?”. That’s where aggregate functions come in! They help us summarize information from our database in a snap. Here are the…

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Aggregate Functions

Imagine you have a big box of LEGO bricks. Sometimes, you want to know just one thing about all those bricks. How many red bricks do you have? Or maybe, if you lined up all your blue bricks, how tall would they be? Well, in the world of computers and databases (think of it as a super-organized digital box!), we have special helper functions that do just that! They look at a whole bunch of…

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Deleting Data

Hey there, young data explorer! 🚀 Today, we’re going to learn about deleting data from a database using the DELETE statement in MySQL. Imagine your database is like a giant notebook where you write down a list of your favorite games, movies, or snacks. But what if you no longer like one of them? You would erase it, right? That’s exactly what DELETE does in MySQL—it removes unwanted data! Let’s…

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Updating Existing Data

Hey there! 👋 Today, we’re going to talk about updating existing data in MySQL using the UPDATE statement. Imagine you have a notebook 📒 where you wrote down your friend’s phone number, but now they have a new one. Instead of erasing the old number and writing a new one, you just update it. That’s exactly what we do in a database with UPDATE! Let’s dive in! 🚀 📌 What is the UPDATE Statement? The…

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Inserting Data into Tables

Imagine you have a big notebook where you write down details about your favorite superheroes. Each page represents a database table, and every row is a new superhero you add to your list. In SQL, we use the INSERT statement when we want to add new information to a table. Let’s explore how we can insert new data into a table using SQL! 🚀 Understanding the INSERT Statement The INSERT statement…

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Persistent Systems' Sr Python Developer Hiring Challenge (2025)

Fitness Challenge (100 Marks) Samantha and Jessica are two sisters who are preparing for their annual fitness challenge. They both have been assigned a personal trainer who has given them a workout plan for the next few weeks. The plan includes a set of N exercises, and for each exercise, there is a recommended number of sets and repetitions. Samantha and Jessica have been keeping track of the…

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Limiting Results with LIMIT and OFFSET

Welcome to another detailed SQL tutorial! Today, we’ll be learning about two important SQL commands, LIMIT and OFFSET, which allows you to control how many rows you get from a database query. This is super useful when working with large datasets and you only want to see a small portion of the results. What is LIMIT? The LIMIT command in SQL helps you limit the number of rows returned by a…

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Sorting Data with ORDER BY

Welcome to today’s SQL course! In this post, we’ll learn how to sort data in SQL using the ORDER BY clause. Sorting helps us organize the results of our queries in a way that makes sense, whether we want to arrange data in ascending or descending order. Let’s start by breaking it down: What is ORDER BY? The ORDER BY clause in SQL is used to sort the results of a query. We can order the results…

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Filtering Data with WHERE Clauses

In SQL, the WHERE clause helps us filter records that match certain conditions. Imagine you’re searching for something in a big box of toys, but you only want the red ones. The WHERE clause is like telling SQL to only give you the red toys. You can use different conditions (like equal to, greater than, or less than) to filter data in many ways. Structure of a WHERE Clause: The basic structure…

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Basic SELECT Queries

Welcome to the world of SQL! Today, we’ll start learning how to use the basic SELECT query. SELECT is one of the most important commands in SQL because it allows you to retrieve or “select” data from a database. Think of a database like a giant bookshelf full of books, and each book contains information. The SELECT query is like the librarian helping you find and read specific books. Let’s dive…

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Writing Your First SQL Query

Welcome to the world of SQL! SQL (Structured Query Language) is a language used to communicate with databases. Imagine a database as a big, organized library full of information. SQL is the tool you use to ask questions and get the exact information you need from that library. In this guide, we will cover: What SQL is and why it’s important How to write your first SQL query Examples of simple…

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SQL Syntax Overview

Welcome to the world of SQL (Structured Query Language)! SQL is the language used to communicate with databases. It helps you store, manage, and retrieve data in a structured way. Think of a database like a huge library, and SQL as the librarian that helps you find the books you want. In this post, we’ll go over the basic structure of SQL and how you can write queries to interact with a…

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Understanding Tables, Rows, and Columns

Imagine you have a big notebook where you keep track of all your favorite toys, video games, and books. This notebook has tables that help you organize everything neatly. Tables are like grids with rows and columns where you can store information. Let’s dive in and understand these in simple terms. 📚 What is a Table? A table in a database is like a spreadsheet. It’s a structured way to organize…

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Connect to a Database Using SQL Clients

Imagine you have a magical library that contains all the books (data) you need. To read these books, you need a special key (connection) to open the library and find the book you want. This is what we do when we connect to a database using SQL clients. In this post, I will show you how to connect to a database step by step, explain some SQL client tools, and provide practice questions and…

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Back up and restore the database

Hey there! Now that you have a test database, it’s time to learn how to back it up (save a copy) and restore it (bring it back if something goes wrong). Imagine this is like saving your favorite video game so you can reload it later if needed. Why Do We Need Backups? Think of your test database like a LEGO castle. If someone accidentally knocks it down, you’d want to rebuild it quickly. A…

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Setting Up a Test Database

Hey there! Today, we’re going to set up a test database step by step, and I’ll make it so simple that even a 10-year-old can follow along. Ready? Let’s go! What is a Test Database? A test database is like a practice notebook for a school test. You use it to try things, learn, and experiment without worrying about breaking anything important. Step 1: Install a Database Management System…