Count how many entries are in a database at 5 minute intervals

问题

I have multiple Raspberry Pi's collecting wifi beacons from mobile devices and save them in a mySQL DB. I have created a view in the DB. Each entry in the DB has the mobile device mac address, the pi id, rssi, location and a timestamp

I have created a view from multiple tables that looks like this.

+----------+--------------+------+-----+---------+-------+
| Field    | Type         | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| pi_id    | varchar(64)  | NO   |     | NULL    |       |
| name     | varchar(127) | NO   |     | NULL    |       |
| location | varchar(255) | NO   |     | NULL    |       |
| mac_id   | varchar(200) | NO   |     | NULL    |       |
| rssi     | int(11)      | NO   |     | NULL    |       |  
| datetime | datetime     | NO   |     | NULL    |       |
+----------+--------------+------+-----+---------+-------+

For each Pi/location I want to count how many packets/beacons were seen during each 5 minute interval. I have been trying something like this.

SELECT datetime , location, count(*) 
FROM packet_locations
GROUP BY DATE(DATE_SUB(datetime, INTERVAL 5 MINUTE)), location;

I want output like this:

+---------------------+----------+----------+
| datetime            | location | count(*) |
+---------------------+----------+----------+
| 2016-01-26 00:00:00 | Pi1      |      44  |
| 2016-01-26 00:00:00 | Pi2      |      66  |
| 2016-01-26 00:05:00 | Pi1      |      100 |
| 2016-01-26 00:05:00 | Pi2      |      101 |
| 2016-01-26 00:10:00 | Pi1      |      128 |
| 2016-01-26 00:10:00 | Pi2      |      128 |
+---------------------+----------+----------+

回答1:

SELECT concat( date_format(datetime,'%Y-%m-%d %k:')
             , lpad(floor(minute(datetime)/5)*5,2,'0')
             , ':00'
             ) datetime
     , location
     , count(1)
  FROM packet_locations
  GROUP BY date(datetime)
         , hour(datetime)
         , floor(minute(datetime)/5)
         , location

来源：https://stackoverflow.com/questions/35096096/count-how-many-entries-are-in-a-database-at-5-minute-intervals

标签

mysql

sql

relational-database