Avoid while loop to check row "state change" - sql-server

Question

I have a table that stores an Id, a datetime and an int crescent value. This value increases until it "breaks" and returns to a 0-near value. Ex: ...1000, 1200, 1350, 8, 10, 25...
I need to count how many times this "overflow" happens, BUT... I'm talking about a table that stores 200k rows per day!
I had already solved it! But using a procedure with a cursor that iterates over it with a while-loop. But I KNOW it isn't the faster way to do it.
Can someone help me to find some another way?
Thanks!
->
Table structure:
Id Bigint Primary Key, CreatedAt DateTime, Value Not Null Int.
Problem:
If Delta-Value between two consecutive rows is < 0, increase a counter.
Table has 200k new rows every-day.
No trigger allowed.
[FIRST EDIT]
Table has the actual structure:
CREATE TABLE ValuesLog (
Id BIGINT PRIMARY KEY,
Machine BIGINT,
CreatedAt DATETIME,
Value INT
)
I need:
To check when the [Value] of some [Machine] suddenly decreases.
Some users said to used LEAD/LAG. But it has a problem... if I chose many machines, the LEAD/LAG fuctions doesn't care about "what machine it is". So, if I find for machine-1 and machine-2, if machine-1 increase but the machine-2 descrease, LEAD/LAG will give me a false positive.
So, how my table actually looks:
Many rows of the actual table
(The image above are selecting for 3 ou 4 machines. But, IN THIS EXAMPLE, the machines are not messed up. But can occurs! And in this case, LEAD/LAG doesn't care if the line above are machine-1 or machine-2)
What I want:
In that line 85, the [value] breaks and restart. Id like to count every occorrence when it happens, the selected machines.
So:
"Machine-1 restarted 6 times... Machine-9 restarted 10 times..."
I had done something LIKE this:
CREATE PROCEDURE CountProduction #Machine INT_ARRAY READONLY, #Start DATETIME, #End DATETIME AS
SET NOCOUNT ON
-- Declare counter and insert start values
DECLARE #Counter TABLE(
machine INT PRIMARY KEY,
lastValue BIGINT DEFAULT 0,
count BIGINT DEFAULT 0
)
INSERT INTO #Counter(machine) SELECT n FROM #Machine
-- Declare cursor to iteract over results of values log
DECLARE valueCursor CURSOR LOCAL FOR
SELECT
Value,
Aux.LastValue,
Aux.count
FROM
ValueLog,
#Machine AS Machine,
#Counter AS Counter
WHERE
ValueLog.Machine = Machine.n
AND Counter.machine = ValueLog.Machine
AND ValueLog.DateCreate BETWEEN #Start AND #End;
-- Start iteration
OPEN valueCursor
DECLARE #RowMachine INT
DECLARE #RowValue BIGINT
DECLARE #RowLastValue BIGINT
DECLARE #RowCount BIGINT
FETCH NEXT FROM valueCursor INTO #RowMachine, #RowValue, #RowLastValue, #RowCount
-- Iteration
DECLARE #increment INT
WHILE ##FETCH_STATUS = 0
BEGIN
IF #RowValue < #RowLastValue
SET #increment = 1
ELSE
SET #increment = 0
-- Update counters
UPDATE
#Counter
SET
lastValue = #RowValue,
count = count + #increment
WHERE
inj = #RowMachine
-- Proceed to iteration
FETCH NEXT FROM valueCursor INTO #RowMachine, #RowValue, #RowLastValue, #RowCount
END
-- Closing iteration
CLOSE valueCursor
DEALLOCATE valueCursor
SELECT machine, count FROM #Counter

Answer 1

Use LEAD(). If the next row < current row, count that occurrence.

Answer 2

Solved using #jeroen-mostert suggested
DECLARE #Start DATETIME
DECLARE #End DATETIME
SET #Start = '2019-01-01'
SET #End = GETDATE()
SELECT
Machine,
COUNT(DeltaValue) AS Prod
FROM
(SELECT
Log.Machine,
Log.Value - LAG(Log.Value) OVER (PARTITION BY Log.Machine ORDER BY Log.Id) AS DeltaValue
FROM
ValueLog AS Log,
(SELECT
Id,
Machine,
Value
FROM
ValueLog
) AS AuxLog
WHERE
AuxLog.Id = Log.Id
AND Proto.DateCreate BETWEEN #Start AND #End
AND Proto.Machine IN (1, 9, 10)
) as TB1
WHERE
DeltaValue < 0
GROUP BY
Machine
ORDER BY
Machine
In this case, the inner LAG/LEAD function didn't mess up the content (what happened for some reason when I created a view... I'll try to understand later).
Thanks everybody! I'm new at DB, and this question make me crazy for a whole day.