Calculate Time Elapsed Between Events

In many applications, understanding the duration between two historical points is crucial for analysis, performance tracking, and business intelligence. This challenge focuses on calculating the time elapsed between two date-time events stored in a database.

Problem Description

You are tasked with writing a SQL query that calculates the difference between two date-time columns, start_time and end_time, for each record in a table named events. The difference should be expressed in a human-readable format, such as "X days, Y hours, Z minutes, W seconds".

Key Requirements:

• Calculate the total duration between start_time and end_time.
• Present the duration in terms of days, hours, minutes, and seconds.
• Handle cases where end_time might be before start_time (though this scenario should ideally be rare and might indicate data quality issues).

Expected Behavior:

The query should return a result set with at least two columns:

1. An identifier for the event (e.g., event_id).
2. A formatted string representing the time difference.

Edge Cases:

• start_time and end_time are the same.
• The difference is less than a full day, hour, minute, or second.
• The difference spans multiple days, weeks, months, or years. (For simplicity in this challenge, we'll focus on days, hours, minutes, and seconds. Consider how to represent larger intervals in a real-world scenario).

Examples

Example 1:

Input Table: events

| event_id | start_time             | end_time               |
|----------|------------------------|------------------------|
| 101      | 2023-10-26 10:00:00    | 2023-10-27 14:30:15    |
| 102      | 2023-11-15 08:00:00    | 2023-11-15 09:15:00    |
| 103      | 2024-01-01 00:00:00    | 2024-01-01 00:00:00    |

Output:

| event_id | duration_formatted     |
|----------|------------------------|
| 101      | 1 days, 4 hours, 30 minutes, 15 seconds |
| 102      | 0 days, 1 hours, 15 minutes, 0 seconds  |
| 103      | 0 days, 0 hours, 0 minutes, 0 seconds   |

Explanation:

• For event_id 101, the difference is 1 day, 4 hours, 30 minutes, and 15 seconds.
• For event_id 102, the difference is 1 hour and 15 minutes.
• For event_id 103, the times are identical, so the difference is zero.

Example 2:

Input Table: events

| event_id | start_time             | end_time               |
|----------|------------------------|------------------------|
| 201      | 2023-12-20 23:50:00    | 2023-12-21 00:10:30    |
| 202      | 2024-02-28 10:00:00    | 2024-03-01 11:00:00    |

Output:

| event_id | duration_formatted     |
|----------|------------------------|
| 201      | 0 days, 0 hours, 20 minutes, 30 seconds |
| 202      | 2 days, 1 hours, 0 minutes, 0 seconds   |

Explanation:

• For event_id 201, the difference crosses midnight. The total duration is 20 minutes and 30 seconds.
• For event_id 202, the duration includes a leap year day (February 29th, 2024) if the database system handles leap years correctly during date calculations. The difference is 2 days, 1 hour.

Constraints

• The start_time and end_time columns are of a DATETIME or TIMESTAMP data type.
• The event_id column is a unique identifier for each event.
• The number of records in the events table can be up to 1 million.
• The SQL dialect used supports standard date and time functions for calculating differences.
• The output duration_formatted string should be a maximum of 100 characters.

Notes

• Most SQL databases provide functions to calculate the difference between two dates. Research your specific database's capabilities (e.g., DATEDIFF, TIMEDIFF, interval arithmetic).
• Consider how to extract the total number of days, remaining hours, remaining minutes, and remaining seconds from the raw difference.
• The formatting of the output string should be consistent and easy to read.
• Pay attention to how your SQL dialect handles time zones if they are relevant to your data. For this challenge, assume all timestamps are in the same, consistent time zone.