How to reduce the value of a column in a row with? - sql

Question

I have a table with two columns:
No Value
1 20
2 10
3 50
4 35
5 17
I also have a variable or parameter where the variables will reduce the value of a column in a row.
So, if my variable V = 5 then my column will update:
No Value
1 15
2 10
3 50
4 35
5 17
Or if V = 50 then:
No Value
1 0
2 0
3 30
4 35
5 17
How can I do that?

Answer 1

First prepare the structure and the data:
CREATE TABLE TAB
(
[No] int identity(1,1) primary key,
[Value] int
);
INSERT INTO TAB VALUES (20);
INSERT INTO TAB VALUES (10);
INSERT INTO TAB VALUES (50);
INSERT INTO TAB VALUES (35);
INSERT INTO TAB VALUES (17);
So now we define your variable to reduce the [Value]:
DECLARE #var int
SET #var = 5
And now you can query your table:
SELECT [No], CASE WHEN [Value] - #var < 0 THEN 0 ELSE [Value] - #var END AS [Value]
FROM TAB
Very easy. You can set your variable to 50 an try again.
Here is a fiddle for this example.

Answer 2

Use CTE can be one of the options
declare #Values table
(
[No] int identity(1,1) not null,
Value int not null
)
declare #DeductAmount int = 50
INSERT #Values VALUES (20), (10), (50), (35), (17)
;WITH cte AS
(
SELECT *,
#DeductAmount - CASE WHEN Value >= #DeductAmount THEN #DeductAmount ELSE Value END AS RemainDeductAmount,
Value - CASE WHEN Value >= #DeductAmount THEN #DeductAmount ELSE Value END DeductedValue
FROM #Values WHERE [No] = 1
UNION ALL
SELECT
v.*,
cte.RemainDeductAmount - CASE WHEN v.Value >= cte.RemainDeductAmount THEN cte.RemainDeductAmount ELSE v.Value END,
v.Value - CASE WHEN v.Value >= cte.RemainDeductAmount THEN cte.RemainDeductAmount ELSE v.Value END DeductedValue
FROM #Values v INNER JOIN cte ON v.[No] = cte.[No] + 1
)
UPDATE target SET Value = DeductedValue
FROM #Values target INNER JOIN cte ON target.[No] = cte.[No]
SELECT * FROM #Values
The secret inside the cte
No Value RemainDeductAmount DeductedValue
----------- ----------- ------------------ -------------
1 20 30 0
2 10 20 0
3 50 0 30
4 35 0 35
5 17 0 17

Answer 3

Change 50 with your variable
Query:
SELECT t.No,
CASE WHEN SUM(t.Value)over(ORDER BY t.No) - 50 <0 THEN 0
WHEN SUM(t2.Value)over(ORDER BY t2.No) > 50
AND SUM(t.Value)over(ORDER BY t.No) >50 THEN t.Value
ELSE SUM(t.Value)over(ORDER BY t.No) - 50
END AS Value
FROM Table1 t
LEFT JOIN Table1 t2 ON t.No - 1 = t2.No

Answer 4

Here is another version:
DECLARE #t TABLE(ID INT IDENTITY(1, 1) , v INT )
DECLARE #x INT = 5
INSERT INTO #t VALUES ( 20 ), ( 10 ), ( 50 ), ( 35 ), ( 17 );
WITH cte
AS ( SELECT * ,
#x - ( SELECT ISNULL(SUM(v), 0) AS v
FROM #t t2
WHERE t2.ID <= t1.ID) s
FROM #t t1
)
SELECT ID ,
CASE WHEN s >= 0 THEN 0
WHEN s < 0 AND v + s > 0 THEN -s
ELSE v END
FROM cte

Answer 5

DECLARE #qty int
SET #qty= 50
WHILE #qty> 0
BEGIN
SELECT #qty= #qty- value
FROM table
WHERE no = (SELECT MIN(no) FROM table WHERE value > 0)
IF #qty< 0
BEGIN
UPDATE table
SET value = ABS(#qty)
WHERE (SELECT MIN(no) FROM table WHERE value > 0)
END
ELSE
BEGIN
UPDATE table
SET value = 0
WHERE (SELECT MIN(no) FROM table WHERE value > 0)
END
END