Question

delimiter $$

CREATE TABLE `tbl_locate` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `Locating` bit(1) DEFAULT NULL,
  `MainPower` bit(1) DEFAULT NULL,
  `Acc` bit(1) DEFAULT NULL,
  `PowerOff` bit(1) DEFAULT NULL,
  `Alarm` int(11) DEFAULT NULL,
  `Speed` int(11) DEFAULT NULL,
  `Direction` int(11) DEFAULT NULL,
  `Latitude` double DEFAULT NULL,
  `Longitude` double DEFAULT NULL,
  `DateTime` datetime DEFAULT NULL,
  `MainID` int(11) DEFAULT NULL,
  `IOState` int(11) DEFAULT NULL,
  `OilState` int(11) DEFAULT NULL,
  PRIMARY KEY (`ID`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=latin1$$

SQL STRING

SELECT * FROM tbl_locate WHERE DateTime=(SELECT MAX(`DateTime`) FROM tbl_locate WHERE MainID=1,2,3)

i want to return the data which is latest row where main id are 1 or 2 or 3,
so,need to return 3 rows latest datetime.
1st row are id 1 latest datetime
second row are id 2 latest datetime
third row are id 3 latest datetime

How to do it?

Answer 1

SELECT        *
FROM          tbl_locate AS a
INNER JOIN     
(
    SELECT    MainID, Max(DateTime) AS DateTime
    FROM      tbl_locate
    GROUP BY  MainID
) AS b
ON            a.MainID = b.MainID
AND           a.DateTime = b.DateTime
WHERE b.MainID in(1,2,3)

try this