how to get this year opening from last year closing with condition? - tsql

Question

I have table of data as below needs to use t-sql to generate
Year | Id | Entitle | Use | Max
-----------------------------------
2016 | 0001 | 15 | 5 | 20
2017 | 0001 | 15 | 2 | 20
2018 | 0001 | 15 | 4 | 20
I need to get opening and closing for each year, this year opening will be last year (opening + Entitle - Use), but it cannot exceed Max, if exceed Max then "Max" will be the opening.
this is the result I expected
year | Id | Opening | Entitle | Use | Max | Closing
-----------------------------------------------------
2016 | 0001 | 0 | 15 | 5 | 20 | 10
2017 | 0001 | 10 | 15 | 2 | 20 | 23
2018 | 0001 | 20 | 15 | 4 | 20 | 31

Answer 1

Here's another option, a recursive CTE will get you there.
DECLARE #TestData TABLE
(
[Year] INT
, [Id] NVARCHAR(10)
, [Entitle] INT
, [Use] INT
, [Max] INT
);
INSERT INTO #TestData (
[Year]
, [Id]
, [Entitle]
, [Use]
, [Max]
)
VALUES ( 2016, '0001', 15, 5, 20 )
, ( 2017, '0001', 15, 2, 20 )
, ( 2018, '0001', 15, 4, 20 );
INSERT INTO #TestData (
[Year]
, [Id]
, [Entitle]
, [Use]
, [Max]
)
VALUES ( 2015, '0002', 20, 7, 20 )
, ( 2016, '0002', 20, 7, 20 )
, ( 2017, '0002', 20, 4, 20 )
, ( 2018, '0002', 20, 13, 20 );
WITH [cte]
AS ( SELECT [a].[Year]
, [a].[Id]
, 0 AS [Opening]
, [a].[Entitle]
, [a].[Use]
, [a].[Entitle] - [a].[Use] AS [Closing]
FROM #TestData [a]
--Cross apply here to get our first record, earliest year for each Id for our anchor
CROSS APPLY (
SELECT [aa].[Id]
, MIN([aa].[Year]) AS [Year]
FROM #TestData [aa]
WHERE [aa].[Id] = [a].[Id]
GROUP BY [aa].[Id]
) [aaa]
WHERE [a].[Year] = [aaa].[Year]
AND [a].[Id] = [aaa].[Id]
UNION ALL
SELECT [c].[Year]
, [c].[Id]
, CASE WHEN [b].[Closing] > [c].[Max] THEN [c].[Max]
ELSE [b].[Closing]
END
, [c].[Entitle]
, [c].[Use]
, CASE WHEN [b].[Closing] > [c].[Max] THEN [c].[Max]
ELSE [b].[Closing]
END + [c].[Entitle] - [c].[Use] AS [Closing]
FROM [cte] [b]
INNER JOIN #TestData [c]
ON [c].[Id] = [b].[Id]
AND [c].[Year] = [b].[Year] + 1 )
SELECT *
FROM [cte]
ORDER BY [cte].[Id]
, [cte].[Year];

Answer 2

Simple SQL will not be enough here. You need to go trough each row and calculate the closing and opening values based on the previous year.
The idea would be to loop trough each row. Store the results. Add the results into a temp table.
I have made you the code here. Please note that I have used SSMS to implement it.
DECLARE #TempTable table (_ID varchar(255),Year int,Opening int, Entitle int,Used int,Max int, Closing int)
DECLARE #idColumn INT
DECLARE #ID varchar(255)
DECLARE #entitle INT
DECLARE #used INT
DECLARE #max INT
DECLARE #opening INT
DECLARE #closing INT
DECLARE #year INT
SELECT #idColumn = min( Id ) FROM MyTable
WHILE #idColumn is not null
BEGIN
SET #year = (SELECT Year FROM MyTable WHERE Id = #idColumn)
SET #ID = (SELECT [_ID] FROM MyTable WHERE Id = #idColumn)
IF #idColumn = 1
BEGIN
SET #entitle = (SELECT Entitle FROM MyTable WHERE Id = #idColumn);
SET #used = (SELECT Used FROM MyTable WHERE Id = #idColumn);
SET #opening = 0;
SET #closing = #opening + #entitle - #used;
SET #max = (SELECT Max FROM MyTable WHERE Id = #idColumn);
END
ELSE
BEGIN
SET #opening = #opening + #entitle - #used;
IF #opening > #max
BEGIN
SET #opening = #max;
END
SET #entitle = (SELECT Entitle FROM MyTable WHERE Id = #idColumn);
SET #used = (SELECT Used FROM MyTable WHERE Id = #idColumn);
SET #max = (SELECT Max FROM MyTable WHERE Id = #idColumn);
SET #closing = #opening + #entitle - #used;
END
INSERT INTO #TempTable (_ID , Year , Opening , Entitle , Used ,Max , Closing )
VALUES (#ID, #year, #opening, #entitle, #used, #max, #closing);
SELECT #idColumn = min( Id ) FROM MyTable WHERE Id > #idColumn
END
SELECT * FROM #TempTable