Question

I have a MySQL query that produces this output ordered like this:

Instead I’d like the output ordered like this:

I’m not sure how to write the query so that it orders the data the way I need it. I need the data sorted by date DESC, then by time DESC, but also to chunk common ‘markers_name’ elements together. (I only want them chunked together for each date).

This is the query I’m using:

SELECT markers.name AS markers_name, 
       conditions.time AS conditions_time, 
       conditions.date AS conditions_date, 
       station.name AS station_name 
FROM markers, conditions, users 
WHERE conditions.markers_id = markers.id 
AND (conditions.station_id = station.id)
ORDER BY date DESC, markers.name, time DESC 
LIMIT 100

(P.S. I omitted showing the station_name in my output tables, but they do show up in my real query.)

EDIT:
I’ve added some more tables in an attempt to explain the problem better.
Note that “chunk” isn’t really returned by the query. I just added that to help with the conversation. Each chunk has a common date.

Here is output after I tried ORDER BY date DESC , markers.name DESC , time DESC

And here is my desired output:

Compare ‘Chunk 4’ in the two outputs. The upper table orders by name descending. This is not desired. Marker_name ‘d’ has the newest information so I want it to be first. ‘C’ has the next newest information. ‘f’ has the oldest information. The next table shows the ordering that I need.

Hopefully this conveys the issue better. Can anyone help?

EDIT 2
I tried this proposed answer: “ORDER BY date DESC, time DESC, markers.name DESC” but it didn’t work.

Note that chunk 3 is ordered by time. The ‘e’ and ‘b’ rows are not grouped together.

Answer 1

Get the list of MAX(time) values for every combination of (markers_id, date) in conditions, then join that list to the rowset you are getting from your present query, and use the MAX(time) values for sorting:

SELECT
  m.name AS markers_name,
  c.time AS conditions_time,
  c.date AS conditions_date,
  s.name AS station_name
FROM markers m
  INNER JOIN conditions c ON c.markers_id = m.id
  INNER JOIN station s    ON c.station_id = s.id
  INNER JOIN (
    SELECT
      markers_id,
      date,
      MAX(time) AS time
    FROM conditions
    GROUP BY
      markers_id,
      date
  ) mx ON c.markers_id = mx.markers_id AND c.date = mx.date
ORDER BY
  c.date DESC,
  mx.time DESC,
  m.name DESC,
  c.time DESC