獲取MySQL數據庫中每個團隊的最後6條記錄

Question

我有一個包含足球結果的MySQL數據庫，並且只想檢索該數據的特定子集。

的數據由含MatchDate，HomeTeam，AwayTeam，HomeGoals一個表，AwayGoals

我怎樣才能獲取該數據包含在過去的6場比賽，各隊已經參與的一個子集？

雖然我可以爲單個團隊做到這一點，但我如何獲得包含表格中每個團隊最近6場比賽的單個子集？ （我不擔心該子集可能包含一些重複項）。

Answer 1

這裏有一種方法用user-defined variable做到這一點：

select MatchDate, HomeTeam, AwayTeam, HomeGoals, AwayGoals 
from (
    select 
    MatchDate, HomeTeam, AwayTeam, HomeGoals, AwayGoals, 
    @teamCounter:=IF(@prevHome=HomeTeam,@teamCounter+1,1) teamCounter, 
    @prevHome:=HomeTeam 
    from yourtable 
    join (select @teamCounter:=0) t 
    order by HomeTeam, MatchDate desc 
) t 
where teamCounter <= 6 

SQL Fiddle Demo

這裏是從小提琴的更新：

select team, MatchDate, HomeTeam, AwayTeam, HomeGoals, AwayGoals 
from (
    select 
    team, yourtable.MatchDate, HomeTeam, AwayTeam, HomeGoals, AwayGoals, 
    @teamCounter:=IF(@prevHome=team,@teamCounter+1,1) teamCounter, 
    @prevHome:=team 
    from yourtable 
    join (
     select distinct matchdate, hometeam team 
     from yourtable 
     union 
     select distinct matchdate, awayteam 
     from yourtable 
    ) allgames on yourtable.matchdate = allgames.matchdate 
     and (yourtable.hometeam = allgames.team or yourtable.awayteam = allgames.team) 
    join (select @teamCounter:=0) t 
    order by team, yourtable.MatchDate desc 
) t 
where teamCounter <= 6 
order by team 

Updated SQL Fiddle

Answer 2

我會使用類似：雖然你真的應該使用

使用（較新的MySQL）

select *,HomeTeam AS HOME from myTable 
where HomeTeam in 
    (select HomeTeam from myTable 
    where Hometeam = HOME 
    order by created_date limit 6) 
group by HomeTeam 

沒有（舊的MySQL）

select * from myTable t1 
where HomeTeam IN 
    (select HomeTeam from myTable t2 
    where t2.HomeTeam = t1.HomeTeam 
     order by created_date 
     limit 6) 
group by t1.HomeTeam 

說明和標籤帶ID在這裏。

如果還沒有，該表應該有一個主鍵。理想地稱爲ID或[table_name] _id。這將使您能夠使用此ID進行子選擇和聯接。永遠不要認爲記錄將是唯一的。作爲一種慣例，使用ID自動遞增主鍵，它會幫助你很多。

Answer 3

你的問題ISN特別是關於主隊還是aw唉團隊，所以我假設一場比賽可以有兩個。

下面的查詢將得到前六場比賽，不管他們打其中：

select MatchDate, HomeTeam, AwayTeam, HomeGoals, AwayGoals 
from (select m.*, 
      (select count(*) 
       from matches m2 
       where (m.hometeam = m2.hometeam or m.hometeam = m2.awayteam) and 
        m.matchdate <= m2.matchdate 
      ) GameCounter 
     from matches m 
    ) m 
where GameCounter <= 6 

它使用相關子查詢拿到了賽。

對於性能，我放棄了相關子查詢的想法。這是從@sgeddes借用想法爲組內的計數：

 select m.* 
     from (select team, matchdate, 
        @teamCounter:=IF(@prevTeam=Team, @teamCounter+1,1) as teamCounter, 
        @prevTeam:=Team 
      from ((select m.hometeam as team, m.* 
        from matches m 
        group by h.hometeam 
       ) union all 
        (select m.awayteam as team, m.* 
        from matches m 
        group by m.awayteam 
       ) 
       ) m cross join 
       (select @teamCounter:=0) const 
      group by team 
      order by team, matchdate desc 
      ) m 
        where TeamCounter <= 6