select id , (value1 + value2)/(select value1 from a where id = t.id - 1)
into b
from a t;
;WITH t AS
(
SELECT rn = ROW_NUMBER()OVER(ORDER BY id), *
FROM a
)
SELECT a.id, (ISNULL(a.value1, 0)+ISNULL(a.value2, 0))/NULLIF(b.value1, 0) AS value
INTO b
FROM t a
LEFT JOIN t b
ON a.rn = b.rn+1
