Question

I got table T1 where I update some counters values

id, unix_time_stamp, counter1, counter10
1 , 1333435800     , 55      , 80

then i got table T2 where i copy those values

id, unix_time_stamp, counter1, counter10, value1, value10
1 , 1333435800     , 55      , 80       , 0     , 0
2 , 1333435801     , 60      , 87       , 5     , 7
3 , 1333435802     , 70      , 90       , 10    , 3
3 , 1333435804     , 80      , 100      , 5     , 5

this is done with some trigger function

INSERT INTO T2 (unix_time_stamp, counter1, counter10) SELECT unix_time_stamp, counter1, counter10 FROM T1 WHERE id=1

What i want is to calculate value1, value10 as a

(current_counter1 - last_counter1)/(current_time - last_time)

and put them in this insert.

for example value 1 with timestamp 1333435804 will be

value1=(80-70)/(1333435804-1333435802) = 5

other words

insert into t2
(unix_time_stamp, counter1, counter10, value1)
SELECT unix_time_stamp, counter1, counter10, 
(counter1 - (select counter1 from T1 order by unix_time_stamp DESC LIMIT 1)/
(unix_time_stamp - (select unix_time_stamp from T1 order by unix_time_stamp DESC LIMIT 1)
FROM T1 WHERE id=1

but i want this in a little shorter version because i got 10 counters 🙂

Whole situation is little bit complicated, and i got some reason to not do this outside SQL

I am using sqlite

This is just to complicated to me 🙂
Please help.

Answer 1

I guess the following query calculates all data you need for your insert clause:

SELECT 1e0 * (cur.counter1 - prv.counter1)/(cur.unix_time_stamp - prv.unix_time_stamp)   AS [value1]
, 1e0 * (cur.counter10 - prv.counter10)/(cur.unix_time_stamp - prv.unix_time_stamp)      AS [value10]
, cur.counter1 AS [cur_counter1], cur.counter10 AS [cur_counter10], cur.unix_time_stamp AS [cur_time]
, prv.counter1 AS [prv_counter1], prv.counter10 AS [prv_counter10], prv.unix_time_stamp AS [prv_time]
FROM T1 cur, T1 prv
WHERE cur.counter1 = (SELECT MAX(aux_0.counter1) FROM T1 aux_0)
AND prv.counter1 = (SELECT MAX(aux_1.counter1) FROM T1 aux_1 WHERE aux_1.counter1 < cur.counter1);