How to Efficiently Select the Most Recent Records in MySQL Based on Multiple Dates?

Selecting the Most Recent Records from a MySQL Table Based on Multiple Dates

In a MySQL table storing data with timestamps, methods, IDs, and responses, the goal is to retrieve the most recent records for each combination of method and ID.

To achieve this, you can utilize the following optimized query:

SELECT *
FROM (
    SELECT *,
    if(@last_method = method, 0, 1) AS new_method_group,
    @last_method := method
    FROM rpc_responses
    ORDER BY method, timestamp DESC
) AS t1
WHERE new_method_group = 1;

This query leverages MySQL variables to avoid the need for a join. It applies the following steps:

1. For each row in the rpc_responses table, it assigns a new group for methods to identify distinct method groups.
2. Rows with the same method belong to the same group.
3. The latest timestamp row within each method group is selected by sorting by method and timestamp in descending order.
4. The query filters the results to only include rows that are the most recent in each method group.

This approach efficiently retrieves the most recent response for each unique combination of method and ID without the need for a join, resulting in optimal performance.

The above is the detailed content of How to Efficiently Select the Most Recent Records in MySQL Based on Multiple Dates?. For more information, please follow other related articles on the PHP Chinese website!