SQL Server : split row into multiple rows based on a column value - sql

Question

I have a question regarding splitting rows based on column value
My example data set is :
id ExpenseType Price
------------------------
1 Car 100
2 Hotel 50
I want to split rows those have some Expense Types such as Car into two rows . Others should remain as one row.
First row Price *70
Second Row Price *30
Returned dataset should be
id ExpenseType Price
-----------------------
1 Car 70
1 Car 30
2 Hotel 50
Thanks for your answers in advance

Answer 1

If you want to split more expense types than car you could use:
WITH r AS (
SELECT 'Car' AS ExpenseType, 0.7 AS Ratio
UNION SELECT 'Car' AS ExpenseType, 0.3 AS Ratio
-- add more ExpenseTypes/Ratios here
)
SELECT
t.id,
t.ExpenseType,
t.Price * ISNULL(r.Ratio, 1.0) AS Price
FROM
your_table t
LEFT OUTER JOIN r ON t.ExpenseType = r.ExpenseType

Answer 2

A simple way uses union all:
select id, expensetype, price
from t
where expensetype <> 'Car'
union all
select id, expensetype, price * 0.7
from t
where expensetype = 'Car'
union all
select id, expensetype, price * 0.3
from t
where expensetype = 'Car';
This is not the most efficient method. For that, a cross apply with filtering logic is better:
select t.id, v.*
from t cross apply
(values (NULL, price), ('Car', price * 0.3), ('Car', price * 0.7)
) v(expensetype, price)
where v.expensetype = t.expense_type or
v.expensetype <> 'Car' and t.expense_type is null;

Answer 3

A less simple way is to use an OUTER APPLY
CREATE TABLE YourSampleData
(
Id INT IDENTITY(1,1) PRIMARY KEY,
ExpenseType VARCHAR(30) NOT NULL,
Price INT NOT NULL DEFAULT 0
);
INSERT INTO YourSampleData
(ExpenseType, Price) VALUES
('Car', 100)
,('Hotel', 50)
,('Gold', 1)
;
SELECT Id, ExpenseType
, COALESCE(a.Price, t.Price) AS Price
FROM YourSampleData t
OUTER APPLY
(
SELECT Price * Perc AS Price
FROM (VALUES
('Car',0.3E0), ('Car',0.7E0)
,('Gold',1.618E0)
) AS v(ExpType, Perc)
WHERE t.ExpenseType = v.ExpType
) a
GO
Id | ExpenseType | Price
-: | :---------- | ----:
1 | Car | 30
1 | Car | 70
2 | Hotel | 50
3 | Gold | 1.618
db<>fiddle here

Answer 4

I ran into a similar need, here is my solution.
Problem statement:
My organization is switching from an in-house build system to a third-party system. Numerical values in the original system surpassed the value size that the destination system could handle. The third-party system will not allow us to increase the field size, as a result we need to split the data up into values that do not surpass the field size limit.
Details:
Destination system can only support values under 1 billion (can include a negative sign)
Example:
DROP TABLE IF EXISTS #MyDemoData /* Generate some fake data for the demo */
SELECT item_no = 1, item_description = 'zero asset', amount = 0 INTO #MyDemoData
UNION SELECT item_no = 2, item_description = 'small asset', amount = 5100000
UNION SELECT item_no = 3, item_description = 'mid asset', amount = 510000000
UNION SELECT item_no = 4, item_description = 'large asset', amount = 5100000000
UNION SELECT item_no = 5, item_description = 'large debt', amount = -2999999999.99
SELECT * FROM #MyDemoData
DECLARE #limit_size INT = 1000000000
DROP TABLE IF EXISTS #groupings;
WITH
max_groups AS
(
SELECT max_groups=100
)
,groups AS
(
SELECT 1 AS [group]
UNION ALL
SELECT [group]+1
FROM groups
JOIN max_groups ON 1=1
WHERE [group]+1<=max_groups
)
,group_rows AS
(
SELECT 0 AS [row]
UNION ALL
SELECT [row]+1
FROM group_rows
JOIN max_groups ON 1=1
WHERE [row]+1<=max_groups
)
,groupings AS
(
SELECT [group],[row]
FROM group_rows
CROSS JOIN groups
WHERE [row] <= [group]
)
SELECT * INTO #groupings FROM groupings;
WITH /* Split out items that are under the limit and over the limit */
t1 AS /* Identify rows that are over the limit and by how many multiples over it is */
(
SELECT
item_no
, item_description
, amount
, over_limit = FLOOR(ABS(amount/#limit_size))
FROM #MyDemoData
)
SELECT /* select the items that are under the limit and do not need manipulated */
item_no
, item_description
, amount = CAST(amount AS DECIMAL(16,2))
FROM t1
WHERE ABS([amount]) < #limit_size
UNION ALL /* select the items that are over the limit, join on the groupings cte and calculate the split amounts */
SELECT
item_no
, item_description
, [Amount] = CAST(
CASE
WHEN row != 0 THEN (#limit_size-1) * ([amount]/ABS([amount]))
ELSE (ABS([amount]) - (t1.over_limit * #limit_size) + t1.over_limit) * ([amount]/ABS([amount]))
END AS DECIMAL(16,2))
FROM t1
JOIN #groupings bg ON t1.over_limit = bg.[group]
WHERE ABS([amount]) >= #limit_size
ORDER BY item_no