malformed. There are many different ways.
Here using a derived table
UPDATE a SET
[totalTime] = sumb.[total]
FROM
TableA AS a
JOIN (
SELECT
b.[id] AS [id]
, SUM(b.[Time_min]) AS [total]
FROM
TableB AS b
GROUP BY
b.[id]
)
AS sumb ON sumb.[id] = a.[ID]
Transact Charlie
Msg 3903.. The ROLLBACK TRANSACTION request has no corresponding BEGIN TRANSACTION.