在MySql中按第一个查询分组

Question

I need to convert the following (sql in access) to mysql. It is a group by first query, but obv mysql can't handle first or last.

SELECT First([20121202].Date) AS FirstOfDate, First([20121202].Time) AS FirstOfTime, [20121202].HomeMatchingId, [20121202].AwayMatchingId, [20121202].RunningStatus
FROM 20121202
GROUP BY [20121202].HomeMatchingId, [20121202].AwayMatchingId, [20121202].RunningStatus
HAVING ((([20121202].RunningStatus)=1))

Basically I am after the time at which the game (hometeam v awayteam) goes in play (runningstatus = 1)

Thanks in advance

Answer 1

Not sure what the date is for, but what about using the regular aggregates?

SELECT 
    MIN(`Date`) AS `FirstOfDate`, 
    MIN(`Time`) AS `FirstOfTime`, 
    `HomeMatchingId`, 
    `AwayMatchingId`, 
    `RunningStatus`
FROM `20121202`
GROUP BY 
    `HomeMatchingId`, 
    `AwayMatchingId`, 
    `RunningStatus`
HAVING 
    `RunningStatus`=1

Answer 2

I assume that the purpose of first is to get the earliest date. If there is at most one row per date, then you can do:

SELECT t.Date AS FirstOfDate, t.Time AS FirstOfTime,
       t.HomeMatchingId, t.AwayMatchingId, t.RunningStatus
FROM `20121202` t join
      (select HomeMatchingId, AwayMatchingId, min(date) as mindate
       from `20121202`
       WHERE RunningStatus = 1;
       group by HomeMatchingId, AwayMatchingId
      ) tmin
      on t.date = tmin.date and t.HomeMatchingId = tmin.HomeMatchingId and
         tmin.AwayMatchingId and t.AwayMatchingId and
WHERE RunningStatus = 1;

I moved the condition on RunningStatus to the where clause, because that is more efficient.