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Learn SQL with me. Made by @csaba_kissi

Joined November 2023
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I prefer available credits
The Mac app now allows you to switch between Used/Available limits
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This is how the deployment flow should look like
CI/CD environment flow, explained clearly ⚙️🚀 Software usually doesn’t go straight from code to users. It moves through a series of environments first 👇 🔹 Development Where features are built, tested locally, and improved fast. 🔹 Testing Where CI runs automated checks to catch bugs early. 🔹 Staging A production-like space for final validation and review. 🔹 Production The live environment used by real customers. Why does this matter? 🛡️ It lowers risk, improves quality, and makes releases afer. Teams can validate changes step by step instead of guessing. Typical path: Code change → testing → staging → production A simple flow, but one of the biggest reasons modern teams ship reliably 📦
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Anti-AI-slop looks cool
nutrient.io - AI document editing with auditable changes ponytail.dev - your AI coding agent writes the least code that works github.com/Nutlope/hallmark - Anti-AI-slop design skill for Claude, Codex motion-primitives.com - reusable animated components cta.gallery - CTA design inspiration
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clianything.cc - Generate a CLI app for AI agents from any program sevalla.com - Deploy apps without managing infrastructure kaneo.app - Open-source self-hosted Linear/Jira alternative reacher.email - Open-source email address checker getlayers.ai - Cinematic AI sites for design inspiration
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SQL Topics Ranked by Difficulty 🧠 🌱 SELECT Statements - Easy 🌱 WHERE Filtering - Easy 🌱 Basic JOINs - Easy 🌱 ORDER BY / GROUP BY - Easy 🌱 Aggregate Functions - Easy ⚙️ Subqueries - Moderate ⚙️ Indexing Strategy - Moderate ⚙️ Transactions & ACID - Moderate
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⚙️ CTEs (WITH clauses) - Moderate ⚙️ Query Optimization - Moderate 🔥 Window Functions - Hard 🔥 Recursive Queries - Hard 🔥 Query Plan Analysis - Hard 🔥 Normalization vs Denormalization - Hard 🔥 Deadlock Handling - Hard
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💀 Sharding & Partitioning at Scale - Very Hard 💀 Multi-Version Concurrency Control - Very Hard 💀 Query Optimizer Internals - Very Hard 💀 Distributed SQL Consistency - Very Hard 💀 Debugging Production Lock Contention - Very Hard Which one would you move up or down? 👀
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Both MySQL and Postgres are great databases.
Backend development is more than building APIs. ⚙️ A simple roadmap: 1️⃣ Learn one language well 2️⃣ Master Git + terminal 3️⃣ Understand HTTP + REST 4️⃣ Pick a backend framework 5️⃣ Learn SQL + databases 6️⃣ Design clean APIs 7️⃣ Add auth + security 🔐 8️⃣ Use caching + queues 9️⃣ Write tests 🧪 🔟 Deploy, monitor, improve 🚀 Core skills: 💻 Code 🗄️ Data 🔌 APIs 🔐 Security 📈 Scalability 📊 Observability Build real projects as you learn. A strong backend developer understands code + data + APIs + security + production.
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DB Indexes are very important. Don't underestimate them.
SQL indexes are one of the simplest ways to make database queries faster. ⚡ (before you start scaling vertically or horizontally) Think of an index like the index at the back of a book: 📖 Without an index: Search → scan rows one by one → find the match 🐢 Gets slower as your table grows 🚀 With an index: Search → check the index → jump directly to matching rows ⚡ Much faster lookups Indexes can help with: 🔎 Faster SELECT queries 📈 Better query performance 💾 Fewer unnecessary disk reads ⚡ Faster filtering and lookups Common index types include: 🔑 Primary index - identifies each row 🛡️ Unique index - prevents duplicate values 📚 Clustered index - controls how data is physically organized 📑 Non-clustered index - keeps a separate lookup structure
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Use IS DISTINCT FROM for NULL-safe comparisons: Unlike <>, it treats NULL as a comparable value: NULL vs NULL → not different NULL vs a value → different two different values → different Supported by PostgreSQL and several other SQL databases.
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SQL tip 💡 Use a window frame to calculate a running total without collapsing rows:
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Use FILTER to calculate multiple conditional aggregates cleanly:
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You can use NULLIF() to prevent division-by-zero errors. When users is 0, NULLIF(users, 0) returns NULL, so the query returns NULL instead of failing.
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10 solid platforms worth checking out for deploying apps, APIs, workers, and databases: • Sevalla • Cloudflare Workers • Fly․io • Vercel • Netlify • Firebase App Hosting • Heroku • DigitalOcean App Platform • Render • Railway
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Which DB type do you prefer?
SQL and NoSQL databases are both essential - but they are built for different kinds of problems. 🗄️⚡ SQL databases are relational. They store structured data in tables with rows and columns. Think: 👤 users 🛒 orders 💳 payments 📊 reports They usually come with: 🔹 predefined schemas 🔹 SQL queries 🔹 joins and relationships 🔹 strong consistency 🔹 transaction support Common SQL databases: 🐘 PostgreSQL 🐬 MySQL 📦 SQLite 🗂️ MariaDB SQL is usually the better choice when: ✅ your data has clear relationships ✅ consistency matters a lot ✅ you need complex queries and reporting ✅ you are building systems like banking, ERP, CRM, or order management NoSQL databases are non-relational. They store data in more flexible formats such as: 📄 documents 🔑 key-value pairs 🧱 wide-column structures 🕸️ graphs Common NoSQL databases: 🍃 MongoDB ⚡ Redis 📡 Cassandra ☁️ DynamoDB NoSQL is often better when: ✅ data structure changes often ✅ you need high throughput ✅ you want to scale horizontally ✅ you are building content feeds, caching layers, real-time apps, or IoT systems A simple mental model: 🟦 SQL = structured + relational 🟧 NoSQL = flexible + scalable Use SQL when relationships, transactions, and data integrity matter. Use NoSQL when flexibility, speed, or large-scale distribution matter most. 🚀
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Finally something related to SQL. Postgres is amazing
Open-source apps for coders kinetics.colorion.co - Open-source CSS/React motion effects with prompts zrok.io - open-source secure local sharing/tunnels scalar.com - modern interactive API docs beszel.dev - open-source, lightweight server monitoring pglite.dev - Lightweight Postgres running in WebAssembly.
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Who else used Redis for cache?
PostgreSQL and Redis are often used in the same application, but they solve very different problems.⚡ PostgreSQL is a relational database designed for durable, structured data. It stores information in tables with rows and columns and supports: 🔹 SQL queries 🔹 Relationships and joins 🔹 Constraints 🔹 ACID transactions 🔹 Complex filtering and reporting Typical PostgreSQL use cases: 👤 User accounts 🛒 Orders and payments 📊 Reports and analytics 🔗 Data with relationships 💾 Long-term business records Redis, on the other hand, is an in-memory data store optimized for extremely fast access. It usually stores data as keys and values: session:123 → active cart:42 → 3 items user:7:role → admin Redis supports structures such as: 🔸 Strings 🔸 Hashes 🔸 Lists 🔸 Sets 🔸 Sorted sets Typical Redis use cases: ⚡ Caching 🔐 Session storage ⏱️ Rate limiting 🔢 Counters 📨 Queues and pub/sub 🕒 Temporary or frequently accessed data The key difference: 🗄️ PostgreSQL = durable source of truth ⚡ Redis = fast access and caching layer A common architecture looks like this: 1️⃣ The app checks Redis 2️⃣ If the data exists, it is returned immediately 3️⃣ If not, the app queries PostgreSQL 4️⃣ The result is stored in Redis for the next request
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Postgres is one of the best databases you can choose. The JSON support it amazing
A clean SaaS stack for shipping faster: Hosting without infra management → Sevalla CDN + WAF → Cloudflare Domains + DNS → Namecheap Auth → Auth0 Database → PostgreSQL Search → Algolia Payments → Paddle Error tracking → Sentry Uptime monitoring → UptimeRobot CI/CD → CircleCI
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Let's hope for SQL tools
Must-know open-source or free tools for coders penpot.app - Open-source UI design platform sevalla.com - Deploy apps without managing infrastructure esponsively.app - preview websites on multiple devices for free ntfy.sh - Open-source push notifications with a simple HTTP call uiverse.io - Free collection of beautiful community-made UI elements
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The power of Docker is in the docker-compose file.
Docker Compose lets you define and run an entire multi-container application from a single compose.yaml file. 🐳 Instead of starting every service manually, you describe how everything should work together: 🌐 Web application 🗄️ PostgreSQL database ⚡ Redis cache 💾 Persistent volumes 🔌 Ports and networking 🔐 Environment variables 🔄 Restart policies 🧩 Service dependencies A typical workflow looks like this: docker compose up -d ➔ start everything docker compose ps ➔ check running containers docker compose logs -f ➔ follow application logs docker compose exec web sh ➔ open a container shell docker compose build ➔ rebuild services docker compose down ➔ stop the stack Think of Docker Compose as the blueprint for your local development or self-hosted application stack. One file defines the infrastructure. One command starts the entire environment. 🚀
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