如何从多个表中查询数据并显示相对于其上次工作日期的每个设备专用的一条记录

Question

Hi I am new to mysql database can any one help to my problem I have three tables like this

select * from device;
Vehiclegroup  vehicleName  deviceid  accountid  
------------  -----------  --------  -----------
sms           cargo        test1      sysadmin   
sms           cargo1       test2     sysadmin   
sms           cargo3       test3     sysadmin   
select * from Account;
accountid  password  deviceid  
---------  --------  ----------
sysadmin   pass      test3     
sysadmin   pass      test2     
sysadmin   pass      test1     
And finally 

mysql> select * from eventdata;
+-----------+-------+----------+----------+
| accountid | speed | date     | deviceid |
+-----------+-------+----------+----------+
| sysadmin  | 45    | 12/10/13 | test3    |
| sysadmin  | 45    | 10/10/13 | test3    |
| sysadmin  | 45    | 10/10/13 | test2    |
| sysadmin  | 45    | 11/10/13 | test2    |
| sysadmin  | 45    | 14/10/13 | test2    |
| sysadmin  | 45    | 17/10/13 | test2    |
| sysadmin  | 45    | 17/10/13 | test1    |
+-----------+-------+----------+----------+
7 rows in set (0.00 sec) 

here i need output table as shown below

vehiclegroup vehiclename deviceid date
sms              cargo1  test1  17/10/13
sms              cargo2  test2  17/10/13
sms              cargo3  test3  12/10/13

ie i need data for each device for the last working date can any one help for this

Answer 1

Something like this?

SELECT d.Vehiclegroup, d.vehicleName, e.deviceid, e.date
FROM eventdata e
INNER JOIN device d ON e.deviceid = d.deviceid
GROUP BY e.deviceid

Will give you one record per deviceid. The Vehiclegroup, vehiclename and date are chosen arbitrary from the list. If you want the latest, you should use a subquery or modifier, like ( MAX(e.date) as date)