`WITH orderedTasks AS (
SELECT AccountID, TaskId, WbsNumber, ROW_NUMBER() OVER (partition by accountid ORDER BY WBSNumber, TaskId) AS NewWbsNumber
FROM TT_Tasks
WHERE AccountId = @accountId
)
UPDATE tt
SET WbsNumber = NewWbsNumber*@maxWBSDelta
FROM orderedTasks tt
OPTION ( OPTIMIZE FOR UNKNOWN )`