Groupwise Max多列

Question

我編寫了一個查詢，使我可以使用groupwise max方法獲取最近的房間。但是，我如何爲多列進行分組最大值？

我有下面的查詢，其中子查詢給我最近的房間，然後加入他們與主表。現在我想挑選下一個將要發生的第一個事件。

例：MIN（DATEDIFF（日，NOW（）））> 0

SELECT name, date, t1.Room, descr, t1.D 
FROM Events 
JOIN 
(
     SELECT Roomid, Room, Latitude, Longitude, 
       ACOS(SIN((:lat))*SIN(RADIANS(Latitude)) + COS((:lat))*COS(RADIANS(Latitude))*COS(RADIANS(Longitude)-(:lon)))*(:R) AS D 
     FROM Rooms 
     WHERE Latitude>(:minLat) AND Latitude<(:maxLat) 
       AND Longitude>(:minLon) AND Longitude<(:maxLon) 
       AND ACOS(SIN((:lat))*SIN(RADIANS(Latitude)) + COS((:lat))*COS(RADIANS(Latitude))*COS(RADIANS(Longitude)-(:lon)))*(:R) < (:rad) 
) AS t1 ON Events.roomid = t1.Roomid 
GROUP BY Room 
ORDER BY D 

有人可以給我如何做到這一點的任何指針？

謝謝！

P.S：事件應該是下一個發生的事件。我不使用ABS（MIN（）），因爲它會返回已經發生的事件。

Answer 1

假設d是您的日期，訂單日期差異和限制1

SELECT name, date, t1.Room, descr, t1.D 
FROM Events 
JOIN 
(
     SELECT Roomid, Room, Latitude, Longitude, 
      ACOS(SIN((:lat))*SIN(RADIANS(Latitude)) + COS((:lat))*COS(RADIANS(Latitude))*COS(RADIANS(Longitude)-(:lon)))*(:R) AS D 
    FROM Rooms 
    WHERE Latitude>(:minLat) AND Latitude<(:maxLat) 
      AND Longitude>(:minLon) AND Longitude<(:maxLon) 
      AND ACOS(SIN((:lat))*SIN(RADIANS(Latitude)) + COS((:lat))*COS(RADIANS(Latitude))*COS(RADIANS(Longitude)-(:lon)))*(:R) < (:rad) 
) AS t1 ON Events.roomid = t1.Roomid 
ORDER BY DATEDIFF(D, now()) 
LIMIT 1