Ecco un approccio alternativo che richiede LAG() che è disponibile da SQL 2012, ma si noti che i dati di esempio non contengono "28 giorni distinti" prima di ogni data. Inoltre, il tipo di dati effettivamente utilizzato non è noto (date/smalldatetime/datetime/datetime2) né se è necessario troncare l'ora dalla data. Quindi, con alcuni avvertimenti, questo approccio crea una serie di intervalli di date per le 28 date distinte (ma i dati non le forniscono, allora sono 28 giorni trascorsi). Ecco una demo di sqlfiddle
Impostazione dello schema PostgreSQL 9.3 :(poiché SQL Server non opera su sqlfiddle)
CREATE TABLE Table1
(theDate timestamp, Value int, promo int, item int)
;
INSERT INTO Table1
(theDate, Value, promo, item)
VALUES
('2011-01-01 00:00:00', 626, 0, 1230),
('2011-01-02 00:00:00', 231, 1, 1230),
('2011-01-03 00:00:00', 572, 1, 1230),
('2011-01-04 00:00:00', 775, 1, 1230),
('2011-01-05 00:00:00', 660, 1, 1230),
('2011-01-06 00:00:00', 662, 1, 1230),
('2011-01-07 00:00:00', 541, 1, 1230),
('2011-01-08 00:00:00', 849, 1, 1230),
('2011-01-09 00:00:00', 632, 1, 1230),
('2011-01-10 00:00:00', 906, 1, 1230),
('2011-01-11 00:00:00', 961, 1, 1230),
('2011-01-12 00:00:00', 361, 0, 1230),
('2012-01-01 00:00:00', 461, 0, 1230),
('2012-01-02 00:00:00', 928, 1, 1230),
('2012-01-03 00:00:00', 855, 0, 1230),
('2012-01-04 00:00:00', 605, 0, 1230),
('2012-01-05 00:00:00', 83, 0, 1230),
('2012-01-06 00:00:00', 44, 0, 1230),
('2012-01-07 00:00:00', 382, 0, 1230),
('2012-01-08 00:00:00', 862, 0, 1230),
('2012-01-09 00:00:00', 549, 0, 1230),
('2012-01-10 00:00:00', 632, 0, 1230),
('2012-01-11 00:00:00', 2, 0, 1230),
('2012-01-12 00:00:00', 26, 0, 1230)
;
Query 1 :
select
t1.item
, ranges.theStart
, ranges.theEnd
, sum(t1.value)
, sum(t1.value) / 28 avg
from (
select
coalesce(lag(theDay,28) over(order by theDay) , theDay - INTERVAL '28 DAYS') as theStart
, theDay as theEnd
from (
select distinct cast(thedate as date) theDay from Table1
) days
) ranges
inner join table1 t1 on theDate between ranges.theStart and ranges.theEnd
group by
t1.item
, ranges.theStart
, ranges.theEnd
| item | thestart | theend | sum | avg |
|------|----------------------------|---------------------------|------|-----|
| 1230 | December, 04 2010 00:00:00 | January, 01 2011 00:00:00 | 626 | 22 |
| 1230 | December, 05 2010 00:00:00 | January, 02 2011 00:00:00 | 857 | 30 |
| 1230 | December, 06 2010 00:00:00 | January, 03 2011 00:00:00 | 1429 | 51 |
| 1230 | December, 07 2010 00:00:00 | January, 04 2011 00:00:00 | 2204 | 78 |
| 1230 | December, 08 2010 00:00:00 | January, 05 2011 00:00:00 | 2864 | 102 |
| 1230 | December, 09 2010 00:00:00 | January, 06 2011 00:00:00 | 3526 | 125 |
| 1230 | December, 10 2010 00:00:00 | January, 07 2011 00:00:00 | 4067 | 145 |
| 1230 | December, 11 2010 00:00:00 | January, 08 2011 00:00:00 | 4916 | 175 |
| 1230 | December, 12 2010 00:00:00 | January, 09 2011 00:00:00 | 5548 | 198 |
| 1230 | December, 13 2010 00:00:00 | January, 10 2011 00:00:00 | 6454 | 230 |
| 1230 | December, 14 2010 00:00:00 | January, 11 2011 00:00:00 | 7415 | 264 |
| 1230 | December, 15 2010 00:00:00 | January, 12 2011 00:00:00 | 7776 | 277 |
| 1230 | December, 04 2011 00:00:00 | January, 01 2012 00:00:00 | 461 | 16 |
| 1230 | December, 05 2011 00:00:00 | January, 02 2012 00:00:00 | 1389 | 49 |
| 1230 | December, 06 2011 00:00:00 | January, 03 2012 00:00:00 | 2244 | 80 |
| 1230 | December, 07 2011 00:00:00 | January, 04 2012 00:00:00 | 2849 | 101 |
| 1230 | December, 08 2011 00:00:00 | January, 05 2012 00:00:00 | 2932 | 104 |
| 1230 | December, 09 2011 00:00:00 | January, 06 2012 00:00:00 | 2976 | 106 |
| 1230 | December, 10 2011 00:00:00 | January, 07 2012 00:00:00 | 3358 | 119 |
| 1230 | December, 11 2011 00:00:00 | January, 08 2012 00:00:00 | 4220 | 150 |
| 1230 | December, 12 2011 00:00:00 | January, 09 2012 00:00:00 | 4769 | 170 |
| 1230 | December, 13 2011 00:00:00 | January, 10 2012 00:00:00 | 5401 | 192 |
| 1230 | December, 14 2011 00:00:00 | January, 11 2012 00:00:00 | 5403 | 192 |
| 1230 | December, 15 2011 00:00:00 | January, 12 2012 00:00:00 | 5429 | 193 |
NB:per SQL Server
- invece di
theDay - INTERVAL '28 DAYS'usa dateadd(day,-28,theDay)
