How to Calculate Total Time Between Earliest and Latest Visits in SQL Using MIN and MAX

Discover how to calculate the total activity time for user visits between the earliest and latest timestamps in SQL without running into aggregate errors.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Calculate total time between earliest and latest visit for all visits

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Calculate Total Time Between Earliest and Latest Visits in SQL Using MIN and MAX

When working with user visits stored in a database, it's crucial to analyze the time spent on different pages effectively. In this guide, we'll tackle a common SQL query problem: calculating the total time spent by users between their earliest visit and their latest activity across different sessions. Let's take a closer look at how to approach this using SQL.

The Problem: Summing Up User Activity Times

Imagine you have a table that logs user visits with columns including timestamps for when the visit was created (page_visit_created_at) and when the last activity occurred (page_visit_last_activity). Your goal is to calculate the total time each user spent on different pages by summing the duration between these two timestamps for each visit.

Consider the following example:

Example Table Structure

iduser_idpagevisit_idpage_visit_created_atpage_visit_last_activity11page1112023-06-21 16:56:13.9502023-06-21 16:58:23.82322page1122023-06-21 17:36:45.5502023-06-21 17:50:23.55331page2112023-06-21 17:01:12.1202023-06-21 17:04:51.12243page1142023-06-21 18:02:13.4212023-06-21 18:09:11.11153page3152023-06-21 18:23:51.3832023-06-21 18:31:11.34761page1162023-06-22 13:10:11.2232023-06-22 13:15:10.111Objective

For instance, for user_id 1, we want to find:

The earliest timestamp for visit_id 11, which is 2023-06-21 16:56:13.950

The latest timestamp for visit_id 11, which is 2023-06-21 17:04:51.122

The total time stemming from both visits

The Challenge

You attempted the following query to calculate the total time per user:

[[See Video to Reveal this Text or Code Snippet]]

However, this resulted in an error message saying, "Cannot perform an aggregate function on an expression containing an aggregate or a subquery."

The Solution: Fixing the Aggregate Error

The key to solving this problem is to separate the calculations into layers. Instead of performing an aggregate function on an already aggregated expression, we can leverage a subquery to first calculate the time spent per visit, then sum those totals by user.

Step-by-Step Query

Here's the corrected SQL query:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Query

Inner Query:

This part (SELECT user_id, visit_id, ... GROUP BY user_id, visit_id) computes the time for each visit by determining the earliest page_visit_created_at and the latest page_visit_last_activity.

DATEDIFF() calculates the difference in seconds between these timestamps.

Outer Query:

After obtaining the time spent for each visit, the outer query aggregates these values by summing them for each user.

GROUP BY user_id ensures we get the total time spent for each unique user.

Conclusion

By successfully using a subquery to handle the aggregation without running into issues, you can efficiently compute the total activity time for each user. This method can be extended or modified to cater to different datasets or additional requirements you may have in your SQL projects.

Feel free to reach out with your questions or experiences with similar SQL challenges! Happy querying!