Split rows into multiple rows based on quantity - sql

Question

I have a rows in my table:
id m_id quantity
1 1 1500
2 1 -1000
3 2 -3000
4 2 2000
5 3 400
6 3 -1000
7 4 500
8 4 -500
9 5 1500
I want to create a view that will return this:
id m_id quantity
1 1 500
2 1 1000
3 1 -1000
4 2 -1000
5 2 -2000
6 2 2000
7 3 400
8 3 -400
9 3 -600
10 4 500
11 4 -500
12 5 1500
View will return equal values in positive/negative and split the rest in a separate rows. So two rows are separated into three rows if positive and negative numbers differ for a given m_id.

Answer 1

I think you can use a query like this:
WITH t1 AS (
SELECT *,
LAG(quantity) OVER (PARTITION BY m_id ORDER BY id) as pq, -- Previous quantity based on id
LEAD(quantity) OVER (PARTITION BY m_id ORDER BY id) as nq -- Next quantity based on id
FROM yourTable
), t2 AS (
SELECT id, m_id, 1 as ord,
CASE
-- If sign is changed and quantity is bigger than that use next quantity
WHEN (SIGN(nq) <> SIGN(quantity)) AND (ABS(quantity) > ABS(nq)) THEN -nq
-- If sign is changed and quantity is bigger than that use previous quantity
WHEN (SIGN(pq) <> SIGN(quantity)) AND (ABS(quantity) > ABS(pq)) THEN -pq
-- Else use original quantity
ELSE quantity
END As quantity
FROM t1
UNION ALL -- Add extra rows
SELECT id , m_id,
CASE
-- Set order to be higher than original quantity
WHEN (SIGN(nq) <> SIGN(quantity)) AND (ABS(quantity) > ABS(nq)) THEN 0
-- Set order to be lower than original quantity
WHEN (SIGN(pq) <> SIGN(quantity)) AND (ABS(quantity) > ABS(pq)) THEN 2
END As ord,
-- quantity is difference
CASE
WHEN (SIGN(nq) <> SIGN(quantity)) AND (ABS(quantity) > ABS(nq)) THEN nq + quantity
WHEN (SIGN(pq) <> SIGN(quantity)) AND (ABS(quantity) > ABS(pq)) THEN pq + quantity
END As quantity
FROM t1
WHERE
-- Find differences more
1 = CASE
WHEN (SIGN(nq) <> SIGN(quantity)) AND (ABS(quantity) > ABS(nq)) THEN 1
WHEN (SIGN(pq) <> SIGN(quantity)) AND (ABS(quantity) > ABS(pq)) THEN 1
ELSE 0
END)
SELECT
-- Use new values for id
ROW_NUMBER() OVER (ORDER BY id, ord) As id,
m_id, quantity
FROM t2;