Identify Session with Maximum Overlapping Sessions Count

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PracHub provides an interactive SQL console where you can write and test queries against real database schemas. Get instant feedback and compare your solution with the expected output.

Q: What difficulty level is this coding question?

This is a medium difficulty Data Manipulation (SQL/Python) question, commonly asked during Onsite rounds at PayPal.

Q: What role is this question designed for?

This question is commonly asked for Data Scientist candidates at PayPal during technical interviews.

Question

sessions

| session_id | start_time           | end_time             |
| 1          | 2023-01-01 09:00:00 | 2023-01-01 10:00:00 |
| 2          | 2023-01-01 09:30:00 | 2023-01-01 11:00:00 |
| 3          | 2023-01-01 10:30:00 | 2023-01-01 12:00:00 |
| 4          | 2023-01-01 13:00:00 | 2023-01-01 14:00:00 |

##### Scenario

SQL screen – session overlap analysis

##### Question

Given the sessions table, write SQL to return the session_id that overlaps with the greatest number of other sessions and the overlap count.

##### Hints

Self-join on intervals where start_a < end_b AND end_a > start_b; aggregate and order by count desc.

PracHub · Accepted Answer

This question evaluates temporal interval reasoning, set-based querying and aggregation skills, focusing on identifying and counting overlapping time intervals using SQL or equivalent Python data-manipulation tools.

Quick Overview

Identify Session with Maximum Overlapping Sessions Count