How to Write Advance SQL Queries | Consecutive Empty Seats | SQL Interview Questions

TL;DR

Learn how to find seats where three or more consecutive seats are empty using lead-lag, advanced aggregation, and a smart method.

Transcript

hi everyone welcome back to the channel today we are going to discuss very interesting problem and it is not just a problem i'm going to solve today the purpose of this video is to tell you advanced concepts so what i will be doing the same problem i will be solving using three method okay first method will be using lead lag second using advanced a... Read More

Key Insights

• 🔍 Advanced concepts in solving a problem using three different methods: lead-lag, advanced aggregation, and a smart approach.
• 💺 Problem statement: Finding all seats where three or more consecutive seats are empty.
• 💡 Lead-lag method: Checking if the previous two or next two rows are empty, along with the current row being empty, to identify consecutive empty seats.
• 💡 Advanced aggregation method: Utilizing advanced aggregation to sum the values of consecutive seats and identify rows where the sum is three, indicating three or more consecutive empty seats.
• 💡 Smart method: Generating a row number and subtracting it from the seat number, then filtering for consecutive differences of the same value, indicating consecutive empty seats.
• 📊 Output: Seven rows containing consecutive empty seats: 4 5 6, 8 9 10 11.
• 🧠 These three methods provide different approaches to solving the problem, showcasing the versatility and creativity in finding solutions.
• 👍 Don't forget to like and share the video, and share your own methods in the comments section.

Questions & Answers

Q: How does the lead-lag function help in identifying consecutive empty seats?

The lead-lag function allows us to check if the previous and next rows are empty, along with the current row, to find three or more consecutive empty seats. It helps compare the seat status across multiple rows using a window function.

Q: How does advanced aggregation simplify the process of identifying consecutive empty seats?

Advanced aggregation enables us to sum the values of the current row, previous two rows, and next two rows. By checking if this sum is equal to three, we can identify groups of three consecutive empty seats more efficiently than checking each seat individually.

Q: What is the advantage of the smart method in finding consecutive empty seats?

The smart method first filters the table to only include rows with empty seats. Then, it generates a row number and calculates the difference between the seat number and the row number. By identifying consecutive seats with the same difference, it efficiently finds groups of three or more consecutive empty seats.

Q: Can the methods shown in the video be applied to similar problems in interviews?

Yes, the methods demonstrated in the video can be applied to various similar problems that involve identifying consecutive empty seats or any pattern in a dataset. They showcase different approaches to problem-solving and can be useful in interview scenarios that test analytical thinking and SQL skills.

Summary & Key Takeaways

• Method 1: Using lead-lag function to check if the previous two rows or the next two rows are empty, along with the current row, to find consecutive empty seats.

• Method 2: Utilizing advanced aggregation to sum the values of the current row, previous two rows, and next two rows and checking if the sum is equal to three to identify consecutive empty seats.

• Method 3: Generating a row number and subtracting the seat number from the row number to determine if the difference is the same for consecutive seats to find groups of three or more consecutive empty seats.