SQLLite time entry and time exit from eventime

Question

I have two tables, DATA and EVENTS, with the following data:

EVENTS
EventIndex  ObjID   LocID   EventData   EventTime       EventType
8         


        

Answer 1

Here is a quick SQL dump for working on the table.

CREATE TABLE EVENTS (EventIndex int, objID int, eventtime datetime);
INSERT INTO "EVENTS" VALUES(83707365,3519434,'2013-05-19 11:32:11');
INSERT INTO "EVENTS" VALUES(83707849,3519434,'2013-05-19 11:35:18');
INSERT INTO "EVENTS" VALUES(83714233,888799,'2013-05-19 12:24:25');
INSERT INTO "EVENTS" VALUES(83714233,888799,'2013-05-19 12:32:18');
CREATE TABLE DATA (eventindex int, tagname char, tagvalue char);
INSERT INTO "DATA" VALUES(83714233,'ObjName','Peter');
INSERT INTO "DATA" VALUES(83714233,'LocName','H118');
INSERT INTO "DATA" VALUES(83715200,'ObjName','Peter');
INSERT INTO "DATA" VALUES(83715200,'LocName','H118');
INSERT INTO "DATA" VALUES(83707365,'ObjName','John');
INSERT INTO "DATA" VALUES(83707849,'ObjName','John');
INSERT INTO "DATA" VALUES(83707365,'LocName','H118');
INSERT INTO "DATA" VALUES(83707849,'LocName','H118');

Step 1, get the maximal and minimal eventtype for each ObjID:

SELECT ObjID, Min(EventIndex) as EventIndex, Min(EventTime) as Entry, Max(EventTime) as Exit
  FROM EVENTS GROUP BY ObjID;


ObjID    EventIndex     Entry      Exit
3519434   83707365   12:24:45  12:32:18
 888799   83714233   11:32:11  11:25:18

Now this reveals some problems with your data structure. For each ObjID, you have two EventIndex, so which one should you pick? Here, I have simply selected the first (smallest) of the two.

Step 2, because sqlite3 dislikes performing operations on aggregates, we make it into a view:

CREATE VIEW single_events AS 
SELECT ObjID, Min(EventIndex) as EventIndex, Min(EventTime) as Entry, Max(EventTime) as Exit FROM EVENTS GROUP BY ObjID;

Step 3, get the total time by operating on the view:

SELECT *, time(strftime('%s', exit) - strftime('%s', entry), 'unixepoch') as total 
  FROM single_events;
ObjID       EventIndex  Entry                Exit                 total
----------  ----------  -------------------  -------------------  ----------
888799      83714233    2013-05-19 12:24:25  2013-05-19 12:32:18  00:07:53
3519434     83707365    2013-05-19 11:32:11  2013-05-19 11:35:18  00:03:07

Step 4, merge this with DATA.

SELECT d1.TagValue as Name, d2.TagValue as Location, Entry, Exit, time(strftime('%s', exit) - strftime('%s', entry), 'unixepoch') as total
  FROM single_events
  LEFT JOIN DATA as d1 USING (EventIndex)
  LEFT JOIN DATA as d2 USING (EventIndex)
  WHERE d1.tagname = 'ObjName' AND d2.tagname = 'LocName';

Of course, if it is a very large data set, you might benefit from pouring d1 and d2 into a temporary table before running step 4.