Creating a view that joins multiple tables on an ID and a timestamp that needs to be rounded - sql

Question

I have a web application that sends data to my sqlite database into different tables depending on the information. I would like to make a view that merges multiple tables together based on cownumber and TS[timestamp] (There are no updates to my table, so a change to the same cownumber send the full record as a new entry with a new timestamp). The ajax calls are made table by table so the TS do not exactly sync up generally they can be 5-20 seconds off depending on the connection
Here is a sample of the three tables
+----master_animal-----+
+----------------------------------------------------+
| cownumber | height | weight | ts |
+-----------+----------+--------+--------------------+
| 1 | 150 | ... | 2017-12-01 12:28:00|
| 2 | 170 | ... | 2017-12-03 17:16:00|
| 3 | 60 | ... | 2017-12-03 08:09:00|
| 4 | 109 | ... | 2017-12-04 23:23:00|
+----animal_inventory-----+
+-------------------------------------------------------------+
| cownumber | brandlocation| dateacquired| ts |
+-----------+--------------+-------------+--------------------+
| 1 | ... | ... | 2017-12-01 12:28:50|
| 2 | ... | ... | 2017-12-03 17:16:30|
| 3 | ... | ... | 2017-12-03 08:09:12|
| 4 | ... | ... | 2017-12-04 23:23:23|
+----experiment-----+
+-------------------------------------------------------------+
| cownumber | ageatwean | birthweight | ts |
+-----------+--------------+-------------+--------------------+
| 1 | ... | ... | 2017-12-01 12:28:20|
| 2 | ... | ... | 2017-12-03 17:16:41|
| 3 | ... | ... | 2017-12-03 08:09:24|
| 4 | ... | ... | 2017-12-04 23:23:11|
The View I wrote
CREATE VIEW testing
AS SELECT a.height,a.weight,a.cownumber,
b.brandlocation,b.dateacquired,
c.ageatwean,c.birthweight
FROM master_animal a, animal_inventory b, experiment c
WHERE a.cownumber=b.cownumber
AND ROUND(a.ts/10000) = ROUND(b.ts/10000)
AND a.cownumber=c.cownumber
AND ROUND(a.ts/10000) = ROUND(c.ts/10000);
The query I wrote
Select * from testing where cownumber = 1;
What I was hoping to get back was
+----testing-----+
+----------------------------------------------------+
| cownumber | height | weight | brandlocation| dateacquired | ageatwean |birthweight |
+-----------+--------+--------+--------------+--------------+-----------+------------+
| 941 | 0 | ... | ... | ... | ... | .. |
Where there will be one row for cownumber 941 as long as all the correlated records were within a few seconds of each other. I am not exactly sure if I need to divide by 10000 or smaller. The same record should be no more than 50 seconds apart from each other. Anything more than 50 seconds apart should be considered a new record.
When I test this where there is only one record for that cownumber it works fine. But lets say I change some information from each table. I provide a new height, a new brandlocation.
Instead of getting two rows. The first row being the initial data entry and the second row showing the same cownumber with the changed values, I get back 8 rows with partial changes.
height|weight|cownumber|brandlocation|dateacquired|ageatwean|birthweight|
0.0|0.0|941|0|0|0.0|0
0.0|0.0|941|0|0|0.0|0
0.0|0.0|941|Left Hip|0|0.0|0
0.0|0.0|941|Left Hip|0|0.0|0
50.0|0.0|941|0|0|0.0|0
50.0|0.0|941|0|0|0.0|0
50.0|0.0|941|Left Hip|0|0.0|0
50.0|0.0|941|Left Hip|0|0.0|0
I assume the issue is in my where clause but I am not sure exactly how to fix it

Answer 1

The timestamps are stored as strings. When you try to divide it, the database tries to convert it to a number, which results in 2017. So all timestamps end up being the same.
Dividing cannot determine the distance; the values 9999 and 10000 will end up different although they are right near each other. (And an integer division results in an integer result, so the ROUND() has no effect.)
To compute the distance, convert the timestamp into a number of seconds first, and then use abs():
SELECT ...
FROM master_animal m
JOIN animal_inventory i ON m.cownumber = i.cownumber
AND abs(strftime('%s', m.ts) - strftime('%s', i.ts)) <= 50
JOIN experiment e ON m.cownumber = e.cownumber
AND abs(strftime('%s', m.ts) - strftime('%s', e.ts)) <= 50;