Articles Cookbook
24 Apr 2025
Jakub Romanowski

The Hidden Cost of bad SQL Queries: Performance and Business Impact

The cost of bad SQL queries isn’t just slow reports or laggy dashboards: it’s wasted server power, higher infrastructure bills, and even frustrated customers when things don’t load fast enough. If your database is working harder than it should, your business is paying the price. Let’s break down how inefficient queries hurt performance and why fixing them matters. Ever had a query that takes forever to run and wondered what's going on?
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22 Apr 2025
LearnSQL.com Team

The Most Useless SQL Queries (and What you Should do Instead)

They run. They return data. But they’re pointless. Here’s what not to write in SQL – and what to do instead. Some SQL queries run just fine – but that doesn’t mean they’re doing anything useful. In this article, we’ll walk through real examples of SQL queries that are valid, harmless-looking, and completely pointless. They waste resources, hide insights, or just add noise. For each one, you’ll see what’s wrong, and how to write a smarter alternative instead.
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17 Apr 2025
Agnieszka Kozubek-Krycuń

Free Databases for Beginners: Where to Start?

Not sure which database to start with? Here are the best free options for beginners along with why they’re great for learning SQL. If you're new to databases, one of the first questions you’ll probably ask is: Which database engine should I start with? With so many options available, it’s easy to feel overwhelmed. SQL databases power everything from small applications to massive enterprise systems, but not all of them are beginner-friendly.
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15 Apr 2025
Scott Davies

Sales Growth Dataset Exploration – Using the Data Analyst Cheat Sheet on Real Sales Data

Have you ever used the Data Analyst Cheat Sheet to analyze a business dataset? In this article, you can see the commands from the cheat sheet in action. I’ll explore a real-world sales dataset to answer 10 key business questions using SQL. Following the guidance from the SQL for Data Analysis Cheat Sheet, I’ll demonstrate how SQL queries can help analyze trends, measure performance, and extract meaningful insights from sales data.
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10 Apr 2025
Jakub Romanowski

Build a Product Inventory Dashboard With SQL

Keeping track of your inventory can be a headache, especially when stock shortages or excess products start causing problems. A product inventory dashboard built with SQL makes it easier to stay on top of stock levels, sales patterns, and reorder points. Instead of guessing when to restock or worrying about over-ordering, you can use data to make smarter decisions. With the right SQL queries, you’ll be able to monitor trends, track sales, and manage your inventory like a pro.
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8 Apr 2025
LearnSQL.com Team

Top 9 Free SQL Practice Resources

Want to sharpen your SQL skills without spending a dime? Here’s a list of the best free SQL practice resources to help you write queries, solve real-world problems, and improve your database expertise – for beginners and advanced users. Learning SQL is essential for anyone working with data, but practicing it effectively can be a challenge – especially if you don’t have access to a database. Fortunately, there are plenty of free SQL practice resources that let you write and test queries in interactive environments, tackle real-world datasets, and even prepare for technical interviews.
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3 Apr 2025
Jakub Romanowski

Converting Data Types in SQL: Essential Techniques for Data Analysts

Converting data types in SQL is an important skill for data analysts who deal with diverse datasets. Whether you're ensuring compatibility between different types of data or optimizing performance, knowing how to handle conversions effectively can save time and prevent errors. This guide explores key SQL data type conversion techniques, explains their real-world applications, and provides practical advice to help you write more efficient queries. By the end, you'll have a clear understanding of how to work with SQL conversions in a way that enhances both accuracy and performance.
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1 Apr 2025
Jakub Romanowski

Course of the Month: Revenue Trend Analysis in PostgreSQL

Updated on: April 1, 2025 Need to understand what your data is saying about your business? In April 2025, our Free SQL Course of the Month is Revenue Trend Analysis in PostgreSQL. Don't miss this opportunity to elevate your analytical capabilities with a leading database system! Understanding revenue trends is crucial for business success, but effective data analysis can be challenging. Dive into the world of SQL reports and enhance your business growth strategies with PostgreSQL.
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1 Apr 2025
Jakub Romanowski

Why Learning SQL Beats Relying on AI: Understanding Data Still Matters

SQL is a fundamental skill for working with data. While AI tools can assist in query generation and automation, they cannot replace the need for human understanding of database structures, query optimization, and data integrity. Knowing SQL ensures better control over your data and helps you make informed decisions. In this article, I will explain why SQL remains an essential skill, even in the AI era. Artificial Intelligence (AI) can generate SQL queries, automate processes, and assist in data management.
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31 Mar 2025
LearnSQL.com Team

New Monthly SQL Practice for April 2025!

Are you a SQL beginner that needs some interactive exercises to practice writing queries? Take up the challenge and choose our April SQL Practice course! In our April 2025 SQL Practice, you’ll meet Olivia, the owner of a hairdressing salon. She needs you to help her gather statistics on the services offered by her salon, the salon customers, their appointments, etc. Can you use your SQL skills to help her find the data?
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