10 Common SQL Mistakes that Cause Performance Issues

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When you're writing SQL queries, sometimes you might not realize you're doing something that could slow everything down. It's like when you're driving, and you take a longer, bumpier route because you didn’t know about the faster one! In this blog, I'll explain some of the most common mistakes people make in SQL queries and how you can avoid them to improve performance. Let’s dive in, with examples using simple Indian names and data!

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Sample Dataset

Imagine we have a table called `Employees` with the following data:

| EmployeeID | Name        | Department | Salary | ExperienceYears |
|------------|-------------|------------|--------|-----------------|
| 1          | Anil Kumar  | IT         | 60000  | 5               |
| 2          | Rani Verma  | HR         | 45000  | 3               |
| 3          | Suresh Gupta| IT         | 75000  | 8               |
| 4          | Meera Patel | Marketing  | 55000  | 4               |
| 5          | Vijay Singh | IT         | 50000  | 2               |

Now, let's explore some common SQL mistakes.