mysql - Filter Rows with time difference -


i have "readings" table columns

  1. timestamp datetime
  2. channel_id integer
  3. value decimal
  4. test_id integer

now want filter rows test_id can do. in result number of rows much. suppose if use channel number 2,3 , 5 test_id 17 , if log data every second there 10k rows.

when plot graph there many data graph lines not visible clearly, make them visible need filter out rows.

i need in filtering of rows time difference between 2 records should few seconds lets 10 seconds. in data not consecutive.

any appreciated.

the sample data follows: 

24-05-2016 08:00:55 | 2 | 10.23  | 17  24-05-2016 08:00:55 | 3 | 100.23 | 17  24-05-2016 08:00:55 | 5 | 12.23  | 17  24-05-2016 08:00:56 | 2 | 09.23  | 17  24-05-2016 08:00:56 | 3 | 12.23  | 17  24-05-2016 08:00:56 | 5 | 11.23  | 17  24-05-2016 08:00:57 | 2 | 09.23  | 17  24-05-2016 08:00:57 | 3 | 01.23  | 17  24-05-2016 08:00:57 | 5 | 11.23  | 17  24-05-2016 08:00:58 | 2 | 09.23  | 17  24-05-2016 08:00:58 | 3 | 01.23  | 17  24-05-2016 08:00:58 | 5 | 11.23  | 17

instead of filtering can aggregate data period using group functionality. example, 10-second periods can calculated timestamps using formula:

round(unix_timestamp(timestamp)/10)

so, formula can added group query, query can aggregate data on period:

select test_id,channel_id,round(unix_timestamp(timestamp)/10),     min(value), max(value), avg(value),count(*) your_table some_conditions gropu test_id,channel_id,round(unix_timestamp(timestamp)/10)

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