Find intersections between rows and timestamps in a mysql db

问题

I have a table, where events of certain objects are listed.

There are two events: "movement" and "load". They can start and end, and these events are listed with timestamps when they happened.

Now i want to calculate the following three numbers:

sum of time, when movement took place (value in the fiddle: 700)
sum of time, when load took place (value in the fiddle: 630)
sum of time, when movement and load took place (value in the fiddle: 611)

I have created a sqlfiddle for the problem here:

http://sqlfiddle.com/#!2/be512

回答1:

The first two columns compute the differences between corresponding end/start events. (Summation is commutative, so we don't need to actually match corresponding events.)

The third colum searches for movement start events for which the preceding load event is a load start event, and for movement end events for which the following load event is a load end event.

SELECT (SELECT SUM(timestamp)
        FROM Table1
        WHERE event = 'movement end') -
       (SELECT SUM(timestamp)
        FROM Table1
        WHERE event = 'movement start') AS all_movement,

       (SELECT SUM(timestamp)
        FROM Table1
        WHERE event = 'load end') -
       (SELECT SUM(timestamp)
        FROM Table1
        WHERE event = 'load start') AS all_load,

       (SELECT SUM(timestamp)
        FROM Table1 a
        WHERE event = 'movement end' AND
              (SELECT event
               FROM Table1 b
               WHERE timestamp = (SELECT min(timestamp)
                                  FROM Table1 c
                                  WHERE c.timestamp >= a.timestamp
                                    AND c.event LIKE 'load %')
              ) = 'load end') -
       (SELECT SUM(timestamp)
        FROM Table1 a
        WHERE event = 'movement start' AND
              (SELECT event
               FROM Table1 b
               WHERE timestamp = (SELECT max(timestamp)
                                  FROM Table1 c
                                  WHERE c.timestamp <= a.timestamp
                                    AND c.event LIKE 'load %')
              ) = 'load start') AS load_movement;

回答2:

Try this

For load answer will be 630 not 690

For the 1st and second case

SELect max(timestamp) - min(timestamp), LEFT(event, LOCATE(' ', event)) 
FROM table1 
group by id, LEFT(event, LOCATE(' ', event));

For 3 rd case

SELect max(timestamp) - min(timestamp), id
FROM table1 
group by id;

FIDDLE

回答3:

this is the query to get the time between start and end:

select sum(a.timestamp-b.timestamp) from Table1 a join Table1 b on a.rowid-b.rowid=1 and a.rowid%2=0 and a.event='movement end';

similary, between end and start:

select sum(a.timestamp-b.timestamp) from Table1 a join Table1 b on a.rowid-b.rowid=1 and a.rowid%2=1 and a.event='movement start';

来源：https://stackoverflow.com/questions/15112004/find-intersections-between-rows-and-timestamps-in-a-mysql-db

标签

mysql

sql

sqlite

postgresql

timestamp