Coding interview preparation

3. Once the calculations are completed, the real DOM updated with only those things which are changed.

2. Now, the difference between the previous DOM representation and the new DOM is calculated.

Virtual DOM works in three steps:

1. Whenever any data changes in the React App, the entire UI is re-rendered in Virtual DOM representation.

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!

Common Data Structure Operations and
Array Sorting Algorithms

It could be useful to have it as a cheat sheet