SQL SELECT Convert Min/Max into Separate Rows - sql

Question

I have a table that has a min and max value that I'd like create a row for each valid number in a SELECT statement.
Original table:
| Foobar_ID | Min_Period | Max_Period |
---------------------------------------
| 1 | 0 | 2 |
| 2 | 1 | 4 |
I'd like to turn that into:
| Foobar_ID | Period_Num |
--------------------------
| 1 | 0 |
| 1 | 1 |
| 1 | 2 |
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
| 2 | 4 |
The SELECT results need to come out as one result-set, so I'm not sure if a WHILE loop would work in my case.

Answer 1

If you expect just a handful of rows per foobar, then this is a good opportunity to learn about recursive CTEs:
with cte as (
select foobar_id, min_period as period_num, max_period
from original t
union all
select foobar_id, min_period + 1 as period_num, max_period
from cte
where period_num < max_period
)
select foobar_id, period_num
from cte
order by foobar_id, period_num;
You can extend this to any number of periods by setting the MAXRECURSION option to 0.

Answer 2

One method would be to use a Tally table, ther's plenty of examples out there, but I'm going to create a very small one in this example. Then you can JOIN onto that and return your result set.
--Create the Tally Table
CREATE TABLE #Tally (I int);
WITH ints AS(
SELECT 0 AS i
UNION ALL
SELECT i + 1
FROM ints
WHERE i + 1 <= 10)
--And in the numbers go!
INSERT INTO #Tally
SELECT i
FROM ints;
GO
--Create the sample table
CREATE TABLE #Sample (ID int IDENTITY(1,1),
MinP int,
MaxP int);
--Sample data
INSERT INTO #Sample (Minp, MaxP)
VALUES (0,2),
(1,4);
GO
--And the solution
SELECT S.ID,
T.I AS P
FROM #Sample S
JOIN #Tally T ON T.I BETWEEN S.MinP AND S.MaxP
ORDER BY S.ID, T.I;
GO
--Clean up
DROP TABLE #Sample;
DROP TABLE #Tally;

Answer 3

Depending on the size of the data and the range of the period, the easiest way to do this is to use a dynamic number fact table, as follows:
WITH rn AS (SELECT ROW_NUMBER() OVER (ORDER BY object_id) -1 as period_num FROM sys.objects)
SELECT f.foobar_id, rn.period_num
FROM foobar f
INNER JOIN rn ON rn.period_num BETWEEN f.min_period AND f.max_period
However, if you're working with a larger volume of data, it will be worth creating a number fact table with an index. You can even use a TVV for this:
-- Declare the number fact table
DECLARE #rn TABLE (period_num INT IDENTITY(0, 1) primary key, dummy int)
-- Populate the fact table so that all periods are covered
WHILE (SELECT COUNT(1) FROM #rn) < (SELECT MAX(max_period) FROM foobar)
INSERT #rn select 1 from sys.objects
-- Select using a join to the fact table
SELECT f.foo_id, rn.period_num
FROM foobar f
inner join #rn rn on rn.period_num between f.min_period and f.max_period

Answer 4

Just Create a function sample date and use it
CREATE FUNCTION [dbo].[Ufn_GetMInToMaxVal] (#Min_Period INT,#Max_Period INT )
RETURNS #OutTable TABLE
(
DATA INT
)
AS
BEGIN
;WIth cte
AS
(
SELECT #Min_Period As Min_Period
UNION ALL
SELECT Min_Period+1 FRom
cte
WHERE Min_Period < #Max_Period
)
INSERT INTO #OutTable
SELECT * FROM cte
RETURN
END
Get the result by executing sql statement
DECLARE #Temp AS TABLE(
Foobar_ID INT,
Min_Period INT,
Max_Period INT
)
INSERT INTO #Temp
SELECT 1, 0,2 UNION ALL
SELECT 2, 1,4
SELECT Foobar_ID ,
DATA
FROM #Temp
CROSS APPLY
[dbo].[Ufn_GetMInToMaxVal] (Min_Period,Max_Period)
Result
Foobar_ID DATA
----------------
1 0
1 1
1 2
2 1
2 2
2 3
2 4