I have the rows below, and i want to access prior row and divide its value by current row. For every row, i need to calculate the Vi value, this Vi value is equal to Vi-1/Vi which means that:
Given the table
Table T
id value out
1 100
2 200
3 10
4 50
I want to generate these values
V1 = 100
V2= 100/200 = 0.5
V3 = 0.5/10 = 0.05
V4 = 0.05/50 = 0.001
So at the end i want the following output:
id value out
1 100 100
2 200 0.5
3 10 0.05
4 50 0.001
I tried using the aggregate function SUM with OVER(), but i do not know how to solve this problem as i need to divide and not sum the value
SELECT id, value, SUM(value) OVER(ORDER BY id ROWS BETWEEN
1 PRECEDING AND 1 PRECEDING ) / value as out
FROM T
Sample data:
CREATE TABLE t(
id INT,
value INT
);
INSERT INTO t VALUES
(1, 100), (2, 200), (3, 10), (4, 50);
Unfortunately, SQL do not have Product
, but it should be simple to use cte. The performance should be not bad if id
was indexed
DECLARE @T table (id int identity(1,1) primary key, value int)
INSERT @T VALUES (100), (200), (10), (50)
;WITH cte AS
(
SELECT id, value, CAST(value AS decimal(20,4)) AS out FROM @T WHERE id = 1
UNION ALL SELECT T.id, T.value, CAST(cte.out / T.value AS decimal(20,4)) FROM cte INNER JOIN @T T ON cte.id = T.id - 1
)
SELECT * FROM cte