Most stressful parts of coding interview

Source: hired.com

How Query is Executed

Order of SQL query execution is not the same as order query is written.
You probably noticed that when you write SELECT count(*) AS column_name, you can't use that column_name in WHERE or GROUP BY clause. It's because select clause in which you defined your alias is not executed yet!

Each query begins with finding the data that we need in a database, and then filtering that data down into something that can be processed and understood as quickly as possible. Because each part of the query is executed sequentially, it's important to understand the order of execution so that you know what results are accessible where.

In general, SQL queries are executed in the following order:

1. FROM: The first step is to identify the tables or views involved in the query. This is specified in the FROM clause of the query.

2. JOIN: If the query involves multiple tables and requires a join operation, the join conditions are evaluated to combine the data from different tables.

3. WHERE: The WHERE clause is applied to filter the rows based on specified conditions. Rows that do not meet the conditions are eliminated from further processing.

4. GROUP BY: If the query includes a GROUP BY clause, the rows are grouped based on the specified columns.

5. HAVING: If a HAVING clause is present, it is applied to filter the groups generated by the GROUP BY clause. Groups that do not meet the conditions are eliminated.

6. SELECT: The SELECT clause is applied to determine the columns to be included in the result set. Any calculations or functions specified in the SELECT clause are also evaluated at this stage.

7. DISTINCT: If the query includes the DISTINCT keyword, duplicate rows are removed from the result set.

8. ORDER BY: If an ORDER BY clause is present, the result set is sorted based on the specified columns.

9. LIMIT/OFFSET: If the query includes a LIMIT and/or OFFSET clause, the result set is limited to a specific number of rows and/or skipped by a certain number of rows.

It’s important to note that not all queries will include every step mentioned above. The order of execution may vary depending on the specific query and the presence of different clauses.

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💡 Tips to Crack Top Tech Companies using LeetCode 💻

Are you aiming to crack top tech companies? Here are some tips on how to effectively use the LeetCode platform to enhance your problem-solving skills and increase your chances of success:

1️⃣ Quality > Quantity ✅

Rather than focusing on solving a large number of problems, prioritize the quality of your solutions. It's better to solve a particular Data Structures and Algorithms (DSA) sheet thoroughly and revise it until you can build up the logic on your own. Consider using resources like the Striver Sheet or Grind 75 to guide your practice.

2️⃣ Maintain an Error Sheet ✅

Create an error sheet to keep track of the questions you've solved and the mistakes you've made while solving them. By reviewing this sheet regularly, you can identify common errors and strive to avoid repeating them. This practice will significantly improve your problem-solving skills over time.

3️⃣ Solve Top Interview Questions ✅

When preparing for a specific company's interview, focus on solving recent LeetCode questions that are tagged with that company's name. This way, you'll be familiar with the types of problems the company typically asks and be better prepared for the interview.

4️⃣ For Beginners ✅

If you're new to problem-solving, it's advisable to start with Easy-level problems before moving on to Medium or Hard ones. Aim to solve at least 25 problems in the Easy category before challenging yourself with more complex ones. This approach helps build a strong foundation and boosts your confidence.

5️⃣ Practice Weak Topics Regularly ✅

Identify the topics or problem types that you find challenging or fear the most. For example, if you struggle with graph problems, make it a habit to solve at least one graph problem every day. Regular practice in your weaker areas will help you improve your skills and boost your overall performance.

6️⃣ Don't Ignore Acceptance Level ✅

When browsing problems on LeetCode, consider sorting them by acceptance level. Prioritizing problems with a higher acceptance rate increases the likelihood of successfully solving them. This strategy allows you to build confidence by tackling problems that have been well-received by other users.

7️⃣ Don't Ignore Other Solutions ✅

Even if your solution is correct and accepted, don't overlook the opportunity to learn from others. Explore alternative solutions to the same problem. This practice exposes you to different approaches, algorithms, and optimizations, enabling you to discover new and efficient ways of solving problems.

8️⃣ Consistency is the Key ✅

Maintain a consistent practice schedule to make steady progress. Dedicate a block of time, such as 2-3 hours each day, to solve LeetCode problems. Additionally, set aside a specific day, like Saturdays, for weekly revisions. Consistency and regular practice will sharpen your problem-solving skills and increase your chances of cracking top tech company interviews.

Good luck with your LeetCode journey! 🚀