MySQL-按时间间隔选择时间范围内的值

Question

I'm trying to select values from a MySQL Table in a time range grouped by a given interval. My actual code looks like this:

SET @dateformat = '%Y-%m-%d %H:%i:%s';
SET @start = '2014-05-07 17:44:15';
SET @stop = '2014-10-27 15:46:58';
SET @interval = 3600;

SELECT  
    t1.id,
    t1.timestamp,
    REPLACE(AVG(t1.A_1), '.', ',') AS avg_val1 
        FROM eco_547702f977d27 AS t1 WHERE timestamp > @start AND timestamp <= @stop GROUP BY UNIX_TIMESTAMP(timestamp) DIV @interval;

This works but groups the values by full hours (18:00, 19:00, 20:00, ...). I want the results to be grouped depending on @start - like 18:44:15, 19:44:15, 20:44:15, ...

Thank You!

Answer 1

You use a very simple trick here :

Add 44:15 to the time value and then do the same GROUP BY , you'll get the data in the required groups

Answer 2

I think the easiest way is just to subtract 44*60 + 15 seconds from the value and use that for the interval arithmetic. Given how you have expressed it:

SELECT t1.id, t1.timestamp, REPLACE(AVG(t1.A_1), '.', ',') AS avg_val1 
FROM eco_547702f977d27 AS t1
WHERE timestamp > @start AND timestamp <= @stop
GROUP BY (UNIX_TIMESTAMP(timestamp) - (44*60 + 15)) DIV @interval;

I would be inclined to put the time in the SELECT :

SELECT t1.id
       FROM_UNIX_TIMESTAMP((UNIX_TIMESTAMP(timestamp) - (44*60 + 15)) DIV @interval) as timestamp,
       REPLACE(AVG(t1.A_1), '.', ',') AS avg_val1 
FROM eco_547702f977d27 AS t1
WHERE timestamp > @start AND timestamp <= @stop
GROUP BY (UNIX_TIMESTAMP(timestamp) - (44*60 + 15)) DIV @interval;