Question

I’m keeping track of some items by inserting records describing these items every hour as a cron job.

I have a table with

steamid(int),
eventid(auto_increment),
itemid(int),
value(int),
time(unix format).

I’m using the hourly statistics to generate a graph to show a 24 hour overview.

Now I’m trying to generate a 7 day historical view.

How can I select the largest value to occur every day for the last 7 days?

Or, if this is easier, how could I perhaps select the first or last entry for each day in the last 7 days?

Thanks in advance.

Answer 1

SELECT   DATE(FROM_UNIXTIME(time)) AS daygroup, 
         MAX(value) AS max_value, 
         MIN(value) AS min_value
FROM     tbl
WHERE    time >= UNIX_TIMESTAMP(CURDATE() - INTERVAL 7 DAY)
GROUP BY daygroup

This will get the minimum and maximum of value for each day in the past 7 days.

Edit: Updated solution to get the data of entire row:

SELECT a.*
FROM tbl a
INNER JOIN
(
    SELECT   DATE(FROM_UNIXTIME(time)) AS daygroup, 
             MAX(value) AS max_value 
    FROM     tbl
    WHERE    time >= UNIX_TIMESTAMP(CURDATE() - INTERVAL 7 DAY)
    GROUP BY daygroup
) b ON DATE(FROM_UNIXTIME(a.time)) = b.daygroup AND a.value = b.max_value