max rows, Sql Server

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declare @CRV_Rooms table(RoomId int, RoomName text);
insert into @CRV_Rooms values
(1, 'Gymnasium'),
(2, 'Conference room'),
(3, 'Boardroom'),
(4, 'Great Hall');

declare @CRV_AttributeLog table(RoomId int, AttributeId text, AnalogValue int, LogTimeStamp datetime);
insert into @CRV_AttributeLog values
(1, 'error_alert',   0, '2017-01-01 15:20'),
(1, 'online_status', 0, '2017-01-01 17:20'),
(1, 'online_status', 2, '2017-01-01 18:20'),
(2, 'error_alert',   0, '2017-01-01 15:20'),
(2, 'online_status', 1, '2017-01-01 20:20'),
(3, 'online_status', 0, '2017-01-01 18:20'),
(3, 'error_alert',   2, '2017-01-01 21:30'),
(3, 'online_status', 0, '2017-01-01 21:40'),
(4, 'error_alert',   2, '2017-01-01 19:20'),
(4, 'error_alert',   2, '2017-01-01 20:20'),
(4, 'online_status', 1, '2017-01-01 20:21');

WITH maxTime as
(
    SELECT   RoomId, MAX(LogTimeStamp) AS LogTimeStamp
    FROM     @CRV_AttributeLog
    WHERE    AttributeID LIKE N'online_status'
    GROUP BY RoomId
)
SELECT  r.RoomName, 
        a.AttributeId, 
        a.AnalogValue,
        m.LogTimeStamp
  FROM  @CRV_AttributeLog a 
  JOIN  maxTime m 
    ON  a.RoomID = m.RoomID
   AND  a.LogTimeStamp = m.LogTimeStamp
   AND  a.AttributeId LIKE N'online_status'
  JOIN  @CRV_Rooms r
    ON  r.RoomId = a.RoomId;

View schema
Execution time: 0,03 sec, rows selected: 4, rows affected: 15, absolute service time: 0,2 sec