SQL Server - Manipulate data and return new results - sql

Question

Is there any way to do something in SQL Server to manipulate data like manipulating arrays in any other programming language?
I have one SQL query that returns 3 columns, "dt_ref" (date), "vlr_venda" (float) and "qt_parcelas" (int)
Basically, I need to do something like this:
- When field "qt_parcelas" is higher than 1, I need to do a "loop" with this row and generate 3 rows.
So, I need to divide the field "vlr_venda" by field "qt_parcelas", and use the field "dt_ref" as reference for the date start and increment month in the date field for the value of "qt_parcelas"
For example, if my query returns these structure:
| dt_ref | vlr_venda | qt_parcelas |
-------------------------------------
|20180901 | 3000 | 3 |
I need to do something to return this:
| dt_ref | vlr_venda |
----------------------
|20180901 | 1000 |
|20181001 | 1000 |
|20181101 | 1000 |
Is it possible to do it in SQL Server?
I've searched for something like this but haven't found anything useful...
Any ideas?

Answer 1

You can use a recursive CTE: Sql Fiddle
with cte as (
select dt_ref, vlr_venda / qt_parcelas as new_val, qt_parcelas, 1 as num
from t
union all
select dateadd(month, 1, dt_ref), new_val, qt_parcelas, num + 1
from cte
where num < qt_parcelas
)
select dt_ref, new_val
from cte;
As written, this will work for up to 100 months. You need to add OPTION (MAXRECURSION 0) for longer periods.

Answer 2

Instead of using a rCTE you could use a tally table. If you have much larger numbers than 3 this'll probably be far be efficient:
WITH N AS(
SELECT n
FROM (VALUES(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL)) N(n)),
Tally AS (
SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) I
FROM N N1 --10 rows
CROSS JOIN N N2 --100 rows
--CROSS JOIN N N3 --Keep adding more CROSS JOINs to create more rows
),
VTE AS (
SELECT CONVERT(date,V.dt_ref) AS dt_ref,
V.vlr_venda,
V.qt_parcelas
FROM (VALUES('20180901',3000,3),
('20181001',12000,6)) V(dt_ref,vlr_venda ,qt_parcelas))
SELECT DATEADD(MONTH,T.I,V.dt_ref),
CONVERT(decimal(10,4),V.vlr_venda / (V.qt_parcelas * 1.0)) --incase you need decimal points
FROM VTE V
JOIN Tally T ON V.qt_parcelas >= T.I;

Answer 3

I developed a software to generate tickets and i had a similar experience than you. I have tried CURSORS and recursive CTE and they all took something like 50 minutes when creating tickets for clients
I used this function to replicate my clients and generate my tickets
/****** Object: UserDefinedFunction [dbo].[NumbersTable] Script Date: 28/09/2018 10:51:25 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE FUNCTION [dbo].[NumbersTable] (
#fromNumber int,
#toNumber int,
#byStep int
)
RETURNS #NumbersTable TABLE (i int)
AS
BEGIN
WITH CTE_NumbersTable AS (
SELECT #fromNumber AS i
UNION ALL
SELECT i + #byStep
FROM CTE_NumbersTable
WHERE
(i + #byStep) <= #toNumber
)
INSERT INTO #NumbersTable
SELECT i FROM CTE_NumbersTable OPTION (MAXRECURSION 0)
RETURN;
END
GO
Then you can use a
CROSS APPLY dbo.NumbersTable(1,qt_parcelas ,1);
To generate your rows
Believe me this way is more efficient and when dealing with large amount of data (something like 8 to 10 million rows) it takes something like 2 minutes instead of 40