Question

我正在玩MySQL实例中的Lahman Baseball Database。我想找到每年超过本垒打（HR）的球员。击球表具有以下（相关部分）的模式：

+-----------+----------------------+------+-----+---------+-------+
| Field     | Type                 | Null | Key | Default | Extra |
+-----------+----------------------+------+-----+---------+-------+
| playerID  | varchar(9)           | NO   | PRI |         |       |
| yearID    | smallint(4) unsigned | NO   | PRI | 0       |       |
| HR        | smallint(3) unsigned | YES  |     | NULL    |       |
+-----------+----------------------+------+-----+---------+-------+

每年，每位玩家都有一个参赛作品（每年数百到12万，可追溯到1871年）。获得一年的前N名击球手很容易：

SELECT playerID,yearID,HR
FROM Batting
WHERE yearID=2009
ORDER BY HR DESC LIMIT 3;
+-----------+--------+------+
| playerID  | yearID | HR   |
+-----------+--------+------+
| pujolal01 |   2009 |   47 |
| fieldpr01 |   2009 |   46 |
| howarry01 |   2009 |   45 |
+-----------+--------+------+

但是我有兴趣从每年年找到前三名。我找到了像this这样的解决方案，描述了如何从类别中选择顶部，并且我尝试将其应用于我的问题，但最终却得到了一个永不返回的查询：

SELECT
    b.yearID, b.playerID, b.HR
FROM
    Batting AS b
LEFT JOIN
    Batting b2
    ON
    (b.yearID=b2.yearID AND b.HR <= b2.HR)
GROUP BY b.yearID HAVING COUNT(*) <= 3;

我哪里出错？

Answer 1

像这样的应该工作：

SELECT b.playerID, b.yearID, b.HR FROM Batting b WHERE HR >= ( SELECT b2.HR FROM Batting b2 WHERE b2.yearID=b1.yearID ORDER BY b2.HR DESC LIMIT 2, 1 ) ORDER BY b.yearID DESC, b.HR DESC;

说明：选择所有具有＆gt; =本垒打数的行作为该年度的第三高行。这不会打破关系。因此，如果不止一个击球手拥有相同数量的全垒打，他们都会出现。

结果是从最近一年订购的，按每年的排名顺序排列。

注意：LIMIT是一个基于0的偏移量，因此2,1表示在第二行抓取一行后开始，即：第三行。

Answer 2

哇，随机。我碰巧在Lahman棒球数据库上使用article模拟Oracle Analytic函数进行相同的查询（但工资虽然）。这个版本的查询非常简洁，但不那么直观。

select *
from (

select 
    b.yearID as year,
    b.teamID as team,
    m.nameFirst as first,
    m.nameLast as last,
    find_in_set(b.HR, x.teamRank) as rank,
    b.HR as HR


from 
    Batting b
    inner join Master m on m.playerID = b.playerID
    inner join (select yearID, group_concat(distinct HR order by HR desc) as teamRank from Batting group by yearID) x on x.yearID = b.yearID

) x

where 
    rank <= 10 and rank > 0 

order by    
    year desc, rank

或者2010年每支球队的前5名人力资源总数......

select *
from (

select 
    b.yearID as year,
    b.teamID as team,
    m.nameFirst as first, 
    m.nameLast as last, 
    b.HR as HR,
    find_in_set(b.HR, x.teamRank) as rank

from 
    Batting b
    inner join Master m on m.playerID = b.playerID
    inner join (select teamID, group_concat(distinct HR order by HR desc) as teamRank from Batting where yearID = 2010 group by teamID) x on x.teamID = b.teamID
where 
    b.yearID = 2010
) x

where 
    rank <= 5 and rank > 0 

order by    
    team, rank

limit 12

显示这些结果......

year    team    first   last        HR  rank
2010    ARI Mark    Reynolds    32  1
2010    ARI Chris   Young       27  2
2010    ARI Kelly   Johnson     26  3
2010    ARI Adam    LaRoche     25  4
2010    ARI Justin  Upton       17  5
2010    ATL Brian   McCann      21  1
2010    ATL Jason   Heyward     18  2
2010    ATL Troy    Glaus       16  3
2010    ATL Martin  Prado       15  4
2010    ATL Eric    Hinske      11  5
2010    BAL Luke    Scott       27  1
2010    BAL Ty      Wigginton   22  2

我怎样每年找到前N名击球手？

2 个答案: