create table dbo.Buckets ( TotalSize int not null, Amount int not null, BucketID int not null,constraint pk_Buckets primary key (BucketID),constraint ck_Buckets_Amount check ( Amount between 0 and TotalSize))go

insert into dbo.Buckets (TotalSize,Amount,BucketID)select 10, 1, 1goinsert into dbo.Buckets (TotalSize,Amount,BucketID)select 5, 4, 2goinsert into dbo.Buckets (TotalSize,Amount,BucketID)select 10, 0, 3goinsert into dbo.Buckets (TotalSize,Amount,BucketID)select 10, 0, 4go

-- The amount of water was have to allocatedeclare @AmountToAllocate intset @AmountToAllocate = 21-- 'Before'select * from dbo.Buckets-- If the amount is positive then we are filling the bucketsif @AmountToAllocate > 0 begin -- Fill these buckets completely, decrease our "amount to allocate" as we go. -- We update just the buckets then we can completely full. If we filled the following bucket then -- we would have exceed the amount of water we have been given to allocate. update dbo.Buckets set Amount = TotalSize, @AmountToAllocate = @AmountToAllocate - (TotalSize - Amount) where Amount != TotalSize and BucketID <= ( select max(B2.BucketID) from dbo.Buckets B2 where @AmountToAllocate >= ( select sum(TotalSize - Amount) from dbo.Buckets B3 where B3.BucketID <= B2.BucketID ) ) -- Part fill the remaining bucket update dbo.Buckets set Amount = Amount + @AmountToAllocate where BucketID = ( select min(B.BucketID) from dbo.Buckets B where B.Amount != B.TotalSize)endelsebegin--We have a negative amount so we are emptying the buckets -- Complete empty buckets update dbo.Buckets set Amount = 0, @AmountToAllocate = @AmountToAllocate + Amount where Amount != 0 and BucketID >= ( select min(B2.BucketID) from dbo.Buckets B2 where abs(@AmountToAllocate) >= ( select sum(Amount) from dbo.Buckets B3 where B3.BucketID >= B2.BucketID ) ) -- Part empty the remaining bucket update dbo.Buckets set Amount = Amount - abs(@AmountToAllocate) where BucketID = ( select max(B.BucketID) from dbo.Buckets B where B.Amount != 0)end--'After'select * from dbo.Buckets

DECLARE @ToAllocate INT = 21;WITH CTE AS (SELECT TotalSize, Amount, BucketID, TotalSize - Amount AS Remaining, SUM(TotalSize - Amount) OVER (ORDER BY BucketID ROWS UNBOUNDED PRECEDING) AS Remaining_RunningTotalFROM dbo.Buckets)SELECT TotalSize, Amount, BucketID, CASE WHEN Remaining_RunningTotal <= @ToAllocate THEN Remaining ELSE @ToAllocate - Remaining_RunningTotal + Remaining END AS AmountToAddFROM CTEWHERE Remaining_RunningTotal - Remaining < @ToAllocateORDER BY BucketID;

DECLARE @AmountToAllocate INT = 21 ;WITH Calculator AS (SELECT BucketID, TotalSize, Amount, AmountLeftToAllocate = CASE WHEN @AmountToAllocate > (TotalSize - Amount) THEN @AmountToAllocate - (TotalSize - Amount) WHEN @AmountToAllocate < 0 AND ABS(@AmountToAllocate) > Amount THEN Amount + @AmountToAllocate ELSE 0 END, NewAmount = CASE WHEN @AmountToAllocate > (TotalSize - Amount) THEN TotalSize WHEN @AmountToAllocate < 0 AND ABS(@AmountToAllocate) > Amount THEN 0 ELSE Amount + @AmountToAllocate END FROM dbo.BucketsWHERE BucketID = 1UNION ALLSELECT tr.BucketID, tr.TotalSize, tr.Amount, AmountLeftToAllocate = CASE WHEN lr.AmountLeftToAllocate > (tr.TotalSize - tr.Amount) THEN lr.AmountLeftToAllocate - (tr.TotalSize - tr.Amount) WHEN lr.AmountLeftToAllocate < 0 AND ABS(lr.AmountLeftToAllocate) > tr.Amount THEN tr.Amount + lr.AmountLeftToAllocate ELSE 0 END, NewAmount = CASE WHEN lr.AmountLeftToAllocate > (tr.TotalSize - tr.Amount) THEN tr.TotalSize WHEN lr.AmountLeftToAllocate < 0 AND ABS(lr.AmountLeftToAllocate) > tr.Amount THEN 0 ELSE tr.Amount + lr.AmountLeftToAllocate END FROM dbo.Buckets trINNER JOIN Calculator lr ON lr.BucketID + 1 = tr.BucketID )SELECT BucketID, TotalSize, Amount = NewAmount, OldAmount = Amount FROM Calculator