Common Data Structure Operations and
Array Sorting Algorithms

It could be useful to have it as a cheat sheet

SQL EXECUTION ORDER

SQL Doesn’t Run the Way You Think It Does!

Most people assume SQL runs top to bottom—
but in reality, the database follows a completely different process.

Here’s what actually happens when you hit Run:

🔹 FROM & JOIN – First, SQL figures out where to pull the data from.
🔹 WHERE – Then, it filters out rows that don’t match your conditions.
🔹 GROUP BY – If needed, it groups the remaining rows together.
🔹 HAVING – Now, it filters those groups (not individual rows).
🔹 SELECT – Finally, it picks the columns you asked for.
🔹 ORDER BY – It sorts the result.
🔹 LIMIT – At the very end, it restricts the output.

Why does this matter?
⤷ You can’t use column aliases in WHERE
because SELECT runs later.
⤷ Filtering after grouping (HAVING)
is less efficient than filtering before (WHERE).
⤷ Understanding this helps you write faster, better queries.

Most analysts assume SQL reads queries like English.
✅ But databases have their own logic—and mastering it makes
you a 10x better analyst!

JOB INTERVIEW CHEAT SHEET

What is JSX?

JSX (JavaScript XML) is a special syntax in React that lets you write HTML-like code inside JavaScript. It makes your code more readable and intuitive because you can describe the UI directly in your JavaScript code.

Why is JSX useful?

✅ Easier to write & read – Looks like HTML but works inside JavaScript.
✅ More powerful than HTML – You can use variables, functions, and logic directly inside JSX.
✅ Optimized by React – JSX gets converted into super-efficient JavaScript calls behind the scenes.
Example of JSX in action:

const name = "Borislav";  
const element = <h1>Hello, {name}!</h1>;  

🚀 Here, {name} is a JavaScript variable inside JSX!

JSX is not HTML – it's just syntactic sugar for React.createElement(). You must wrap elements properly (e.g., use one parent tag).

Want to build awesome React apps? JSX is the way to go! 🔥

API Protocols

What do you understand by Virtual DOM?

Think of the Virtual DOM like a draft version of your web page. Instead of changing the actual page (which is slow), React updates this lightweight copy first. Then, it smartly compares the draft with the real page and updates only the necessary parts kind of like editing a document without retyping the whole thing.

Result? Faster updates, smoother performance, and a better user experience! 🚀