Det finns en (mer eller mindre) känd teknik för att lösa den här typen av problem, som involverar två ROW_NUMBER()
samtal, så här:
WITH marked AS (
SELECT
*,
grp = ROW_NUMBER() OVER (PARTITION BY product ORDER BY date)
- ROW_NUMBER() OVER (PARTITION BY product, price ORDER BY date)
FROM #ph
)
SELECT
product,
date_from = MIN(date),
date_to = MAX(date),
price
FROM marked
GROUP BY
product,
price,
grp
ORDER BY
product,
MIN(date)
Utdata:
product date_from date_to price
------- ---------- ------------- -----
1 2012-01-01 2012-01-04 1
1 2012-01-05 2012-01-08 2
1 2012-01-09 2012-01-12 1