How to Find the Most Recent Record in Each Group Using SQL's GROUP BY?

Locating Recent Records in Each Group with GROUP BY

To identify the most recent record within each group categorized by a specific column, such as sender ID, there are two options to consider:

Option 1: Determining Last Timestamp Values

This technique involves finding the latest timestamp value for each group. A sample query for this approach is:

SELECT from_id, MAX(timestamp) timestamp FROM messages GROUP BY from_id

Option 2: Joining on Calculated Values

Another method is to combine the original table with the results of the subquery that determines the maximum timestamp for each group. The following query exemplifies this approach:

SELECT t1.* FROM messages t1
JOIN (SELECT from_id, MAX(timestamp) timestamp FROM messages GROUP BY from_id) t2
ON t1.from_id = t2.from_id AND t1.timestamp = t2.timestamp;

By utilizing either of these methods, you can retrieve the latest message for each distinct sender ID, providing a more comprehensive view of the most recent conversations.

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