I'm just pointing out two ways in which you can make your system non-ACID.
1) Leave it on the default isolation level (READ_COMMITTED):
You have ten accounts, which sum to $100. You know your code cannot create or destroy money, only move it around. If no other thread is currently moving money, you will always see it sum to $100. However, if another thread moves money (e.g. from account 9 to account 1) while your summation is in progress, you will undercount the money. Perfectly legal in READ_COMMITTED. You made a clean read of account 1, kept going, and by the time you reach account 9, you READ_ what the other thread _COMMITTED. Nothing dirty about it, you under-reported money for no other reason than your transactions being less-than-Isolated. You can then take that SUM and cleanly write it elsewhere. Not dirty, just wrong.
2) Use an ORM like LINQ. (Assume FULL ISOLATION - even though you probably don't have it)
If you were to withdraw money from the largest account, split it into two parts, and deposit it into two random accounts, you could do it ACID-compliantly with this SQL snippet:
SELECT @bigBalance = Max(Balance) FROM MyAccounts
SELECT @part1 = @bigBalance / 2;
SELECT @part2 = @bigBalance - @part1;
..
-- Only showing one of the deposits for brevity
UPDATE MyAccounts
SET Balance = Balance + @part1
WHERE Id IN (
SELECT TOP 1 Id
FROM MyAccounts
ORDER BY NewId()
);
// Split the balance in two
var onePart = maxAccount.Balance / 2;
var otherPart = maxAccount.Balance - onePart;
// Move one half
maxAccount.Balance -= onePart;
recipient1.Balance += onePart;
// Move the other half
maxAccount.Balance -= otherPart;
recipient2.Balance += otherPart;
info: 1/31/2026 17:30:57.906 RelationalEventId.CommandExecuted[20101] (Microsoft.EntityFrameworkCore.Database.Command)
Executed DbCommand (7ms) [Parameters=[@p1='a49f1b75-4510-4375-35f5-08de60e61cdd', @p0='1845'], CommandType='Text', CommandTimeout='30']
SET NOCOUNT ON;
UPDATE [MyAccounts] SET [Balance] = @p0
WHERE [Id] = @p1;
SELECT @@ROWCOUNT;If you are running in RC isolation, and perform a select sum() from table, you are reading values committed by other threads BEFORE the select statement began, you are not getting other threads committed values during the select, you are not breaking ACID.
If you are suggesting that running a simple BEGIN; select sum() from table; COMMIT is breaking acid in a default RC level, you are wrong and should best avoid commenting on isolation levels in RDBMS online, to not confuse people further.
If you are however suggesting that we are breaking ACID if we do app side stupidity such as:
value1=BEGIN; SELECT value from table where id=1;commit value2=......
sum = value1+value2....+value10
Then yes obviously its not acid but nobody in their right minds should be doing that. Even juniors quickly learn that this is incorrect code.
If you are suggesting we do repeatable reads in RC then yes its obviously not ACID but your example does not mention repeatable summations only a single one.
They originally arose as tool, but complex numbers are fundamental to quantum physics. The wave function is complex, the Schrödinger equation does not make sense without them. They are the best description of reality we have.