Vlastní výpočet částky

Zde je alternativní přístup, který vyžaduje LAG(), který je k dispozici od SQL 2012, ale všimněte si, že ukázková data neobsahují „28 odlišných dnů“ před každým datem. Také není znám skutečný použitý datový typ (date/smalldatetime/datetime/datetime2), ani není známo, zda je potřeba zkrátit čas od data. S určitými výhradami tedy tento přístup vytváří řadu období pro 28 různých dat (ale pokud je data neposkytují, pak jde o 28 uplynulých dní). Zde je ukázka sqlfiddle

Nastavení schématu PostgreSQL 9.3 (protože SQL Server nefunguje na 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)
;

Dotaz 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

Výsledky :

| 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 |

Poznámka:Pro SQL Server

• místo theDay - INTERVAL '28 DAYS' použijte dateadd(den,-28,den)