How to Find the Maximum Date in a MySQL Join?

How to Select the Maximum Date Within a Join Statement

In MySQL, it is possible to retrieve the maximum date for a particular attribute within a joined dataset using the MAX() function. This technique is commonly employed to gather historical data or identify the most recent instance of a specific event.

Consider the following query:

SELECT t1.received_id
     , t1.transaction_id
     , t1.date_modified
     , l.location
  FROM transactions t1
  JOIN ( SELECT received_id, MAX(date_modified) maxmodify FROM transactions GROUP BY received_id) max_record
    ON max_record.received_id = t1.received_id 
   AND max_record.maxmodify = t1.date_modified
  JOIN locations l
    ON l.location_id = t1.location_id
  JOIN received r
    ON r.received_id = t1.received_id
 WHERE t1.received_id = '1782'
 ORDER 
    BY t1.date_modified DESC

This query retrieves the receipt ID, transaction ID, date modified, and location for the record with ID '1782', where the date modified matches the maximum date found for that receipt ID. This ensures that we obtain the latest historical information for the specified record.

The core component of the query is the following subquery:

SELECT id,MAX(thing) max_thing FROM my_table GROUP BY id

This subquery identifies the maximum value for the thing attribute within each group defined by the id attribute. By joining the original table with this subquery, we can filter out records with non-maximum dates, thereby retrieving only the desired historical data.

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