SQL/MySQL learning series: Day 3️⃣

👋 Welcome to day 3 of our SQL series

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📌 Lesson 3: SQL vs MySQL vs PostgreSQL vs Oracle vs MariaDB vs SQLite – Understanding the Differences 🚀

👋 Now that we know what SQL is, let’s explore the different database systems that use SQL.


You know that SQL is a language for talking to databases, right? But SQL itself is NOT a database. It’s just the way we send commands.

The actual databases—like MySQL, PostgreSQL, SQLite, and Oracle—are the systems that store and manage data. They all understand SQL, but each has its own special features.

So, let’s break them down! 🧐

🟢 What They Have in Common

No matter which database you use, SQL lets you:
✅ Store data in tables 📂
✅ Retrieve data with SELECT 🔍
✅ Insert new data with INSERT ✏️
✅ Update existing data with UPDATE 🔄
✅ Delete data with DELETE ❌

That means if you learn SQL once, you can use it in ANY of these databases! 🙌

But… there are some differences. Let’s compare them!


🟢 Breaking it Down: When to Use Each Database?

🔹 MySQL – Best for web applications (e.g., WordPress, Facebook).
🔹 PostgreSQL – Great for complex queries, data analytics, and apps needing JSON support.
🔹 Oracle DB – Used in banks, large enterprises, and high-security systems.
🔹 SQLite – Ideal for mobile apps and small projects (e.g., Android, iOS apps).
🔹 MariaDB – A faster, open-source alternative to MySQL, often used in place of MySQL.

—————————————————

🟢 SQL vs Database Management Systems (DBMS)

Let's clear this confusion as well.
SQL is just a language, but to store and manage data, we need a database system. Think of it like this:

💬 SQL = Language 🗣
💾 Database = Storage System 🏛

Different databases use SQL, but they have unique features. Let’s compare the most popular ones.

—————————————————

🟢 Example Queries – Do They Work Everywhere?

Most of the syntax is the same across these databases since they all use SQL as the base language. However, there are some small differences in advanced features, functions, or performance optimizations specific to each database. Let’s look at some example queries to see how they might differ.

🔹 Basic Query (Works Everywhere)

SELECT * FROM customers WHERE city = 'London';

🔹 JSON Query (PostgreSQL Only)

SELECT data->>'name' AS name FROM customers;

🔹 Limiting Results (Different Syntax)
✅ MySQL, PostgreSQL, SQLite, MariaDB:

SELECT * FROM customers LIMIT 5;

✅ Oracle:

SELECT * FROM customers FETCH FIRST 5 ROWS ONLY;

As you can see there are not many differences between those when it comes to syntax 😊
—————————————————

🟢 So, Which One Should You Learn?

👨‍💻 Just starting out? → MySQL or PostgreSQL are great choices.
📊 Working with analytics? → PostgreSQL is your friend.
🏦 Enterprise work (banks, big companies)? → Oracle DB is common.
📱 Mobile apps or small projects? → SQLite is perfect.
🚀 Looking for a MySQL alternative? → MariaDB is worth checking out.

No matter which one you pick, the SQL basics are the same.

—————————————————

🟢 Key Takeaways
✅ SQL is universal, but different databases have different features.
✅ MySQL is great for web apps, PostgreSQL is powerful for large applications.
✅ SQLite is lightweight, Oracle DB is enterprise-level, and MariaDB improves on MySQL.
✅ Most basic SQL commands work across all databases.

📌 Next Lesson: Setting Up Your First Database – Installing MySQL & PostgreSQL. Stay tuned! 🚀

If you like this way of learning show some love ❤️

Here are some additional info about previous SQL database types lesson

SQL/MySQL learning series: Day 4️⃣

Sorry guys I was on a trip for previous few days so there was no new courses during previous week but now its time for:

💥 Day 4 of our SQL series 💥

📘 Lesson 4: Setting Up SQL – Install MySQL/PostgreSQL & Set Up Workbench or DBeaver

Before writing your first SQL query, you need a database to work with — and a nice interface to explore it. Here’s a simple guide to setting up your environment:

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🔹 Step 1: Choose your database system
The most popular free options are:

• MySQL – Beginner-friendly and widely used in web development.
• PostgreSQL – Open-source, powerful, and great for more complex work.
> If you're just starting out: go with MySQL.
> If you're curious about more advanced features: try PostgreSQL.

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🔹 Step 2: Install the database

✅ For MySQL:
• Download: [https://dev.mysql.com/downloads/](https://dev.mysql.com/downloads/)
• Install using the MySQL Installer.
• Set a root password (don’t forget it!).

✅ For PostgreSQL:
• Download: [https://www.postgresql.org/download/](https://www.postgresql.org/download/)
• Use the installer for your OS.
• Set a password for the "postgres" user during install.

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🔹 Step 3: Install a database interface (GUI)

Instead of using a terminal, you can write queries in a clean, visual tool:

• MySQL Workbench (for MySQL only)
→https://www.mysql.com/products/workbench/

• DBeaver (works with MySQL, PostgreSQL & many others)
→ https://dbeaver.io/

Both are 100% free.

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🔹 Step 4: Connect the GUI to your database

In the app you installed:
• Click New Connection
• Choose MySQL or PostgreSQL
• Host: localhost
• Port: 3306 (MySQL) or 5432 (PostgreSQL)
• Username: root (MySQL) or postgres (PostgreSQL)
• Password: the one you just created

Test the connection – if it says "Success", you’re ready! ✅

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💡 No install? Try online playgrounds
If you want to play with SQL right now without setting up anything:

• db-fiddle
• sqlime

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Once you’re all set up, let’s move on to writing your first queries!

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🌸🐣 Happy Easter from the World of Code & Data! 🐰💻

May your day be filled with joy, colorful moments, and beautifully structured queries.
Wishing you and your loved ones a warm, happy, and meaningful Easter!

Your @bigdataspecialist

How discord stores trillions of messages 🧠

An interesting video about one of the biggest challenges in tech world.

This video breaks it down - from the databases they use, to the smart engineering choices that keep everything running smoothly at scale.

No fluff, just a super interesting look at how one of the biggest chat platforms actually works behind the scenes.

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If you're into system design, scalability, or backend engineering, this one’s a must-watch.

Link

Sorry for not posting for a long time.
I am getting ready for my wedding which will happen in 10 days!🤵👰

Also I will be attending Data Science/AI conference in Malaga (Spain) this week: https://jonthebeach.com/

If you are going to be there please come to say hello 😊

I just got married guys! 😍

This is me and my wife at sunset on our wedding day.

After conference in Spain i come back home and had most amazing wedding 💫

Thanks everyone for your patience. I will start posting regularly soon.

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You’ll commonly work with:
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---

📚 Free Materials & Docs:

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---

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🔹 SQL Series: Day 5️⃣ – Database & Table Basics

👋 Hey folks! After a few weeks’ break, we’re back with our Monday SQL series specials.
WE are still at basics, today we'll dive into the core building blocks of any database. Think of this as learning the ABCs before writing epic SQL novels.

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🏛 What’s a Database?
A “digital filing cabinet” that holds tables of related info (Users, Products, Orders…).

📋 Tables = Supercharged Spreadsheets
Organized into columns (fields) and rows (records), modeling one real-world entity each.

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+----+---------+-----------------------+  
| id | name    | email                 |  
+----+---------+-----------------------+  
| 1  | Alice   | [email protected]     |  
| 2  | Bob     | [email protected]       |  
| 3  | Carol   | [email protected]     |  
+----+---------+-----------------------+  

* Columns 🔹 Header labels (id, name, email) define the type and name of each data slot—like spreadsheet headers.
* Rows 🔸 Each line is one record (e.g., (2, Bob, [email protected])), representing a single entity.
* Cells ⚡️ Intersection of row+column; e.g., Bob’s email is [email protected].

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🔹 Column types

They tell the database what kind of data each column holds (numbers, text, dates, etc.). Think of them as choosing the right container—glass for water, plastic for cereal.

-—

📚 Column Types at a Glance

* INT – Whole numbers (IDs, counters)
* VARCHAR(n) – Variable-length text up to *n* characters (names, emails)
* DECIMAL(p,s) – Exact decimals with *p* total digits and *s* after the dot (prices, quantities)
* DATE / DATETIME – Calendar dates or timestamps (order dates, signup times)

🔍 Why? Choosing the right type:
• ✅ Saves space (no storing “300 characters” in a “10-char” field)
• ✅ Speeds up comparisons & calculations


That's it for today, next Monday we talk about primary keys 🔑
Please leave reactions to this post if you find this valuable ❤️

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🔹 SQL Series: Day 6️⃣ – Mastering the Primary Key

👋 Hey data adventurers! Today we’re shining the spotlight on the Primary Key - the VIP pass that makes every row unique and lightning-fast to find.

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🛠 Origins: Why Primary Keys Were Born

* Prevent Duplicate Records: In early systems, it was all too easy to accidentally insert “two Alices” primary keys ensure each record stays one-of-a-kind.
* Enable Fast Access: As datasets grew, scanning millions of rows was impractical. Keys provided a built-in index for instant lookups.
* Support Relationships: To link data across tables reliably (think Orders → Customers), you need a stable, unique anchor.

---

+----+---------+-----------------------+  
| id | name    | email                 |  
+----+---------+-----------------------+  
| 1  | Alice   | [email protected]     |  
| 2  | Bob     | [email protected]       |  
| 3  | Carol   | [email protected]     |  
+----+---------+-----------------------+  

🔑 What Makes a Primary Key Special?

* Unique – No two rows share the same value.
* Not NULL – Every record must have one.
* Indexed – The database auto-builds an index, so WHERE id = 2 is blazing fast.
* Integrity Enforcer – Prevents duplicates and anchors foreign-key relationships.

---


📋 1. Only One per Table
A table can have just one primary key.

> Even if it’s made of multiple columns (a composite key), you still pick *one* PK to enforce uniqueness.

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🧩 2. Composite Primary Keys
When no single column does the job, team up two (or more) columns:

PRIMARY KEY (order_id, product_id)

This combo ensures each row is unique only when both values match.

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🌱 3. Natural vs. Surrogate Keys
Primary key can be natural or surrogate key:
* Natural Key: Real-world data (e.g., email).
* Surrogate Key: System-generated (e.g., AUTO_INCREMENT or a UUID).

> Tip: Surrogates stay stable; naturals can change (and bite you!).

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🛡 4. Best Practices
• Stable – Pick values that won’t change.
• Minimal – Keep it short; every byte counts.
• Simple – One-column PKs are easiest; use composites only when needed.

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🔐 While the Primary Key is our star today, remember there’s a whole key family waiting in the wings: Super Keys, Candidate Keys, Alternate Keys, Composite Keys, Unique Keys, Foreign Keys, Surrogate Keys… we’ll dive into those soon!

Bash brackets cheat sheet

For all those bash people out there, this might be useful

Man gotta love bash, right? 😁