Question

我有两个类型（类型，播放器）和播放器（播放器，日期）的表我必须每年都能找到有多少人参加比赛，哪种类型的球员获胜？

例如表格应该像

year type      noofawards
2011 batsmen       3
2011 bowler        5
2010 batsmen       2

我可以获得每年赢得的奖项总数，但不能将它们分类，所以我得到的是

year noofawards
2011     3 


select year , count(year) as "Number of awards"
from
(
select to_char(p.date,'YYYY') as year 
from player p, type t
where p.playerid = t.playerid
)
group by year
order by year;

我该怎么办？

Answer 1

您是否尝试过以下操作：

select to_char(p.date,'YYYY') as year
     , type
     , count(*)
from player p, type t
where p.playerid = t.playerid
group by 1,2;

Answer 2

只需使用：

GROUP BY year
       , type

大多数数据库系统都有一个函数（YEAR()或类似的名称）来从日期中提取年份。
拥有保留的字段或表名称，如date不是一个好主意。
您还应该尝试学习JOIN语法而不是WHERE的隐式联接。

类似的东西：

SELECT YEAR(p.date) AS awardYear
     , t.type
     , COUNT(*) AS "Number of awards"
FROM player p
  JOIN type t
    ON p.playerid = t.playerid
GROUP BY awardYear
       , t.type
ORDER BY awardYear
       , t.type ;

Answer 3

由于这个家庭作业的尖叫，我只会给出提示。

您不需要使用子查询，您需要在查询中的某个位置实际选择“类型”列。

Answer 4

这应该有效：

SELECT year,
       type,
       COUNT(*) as number
FROM (
       SELECT type,
              to_char(player.date,'YYYY') as year
       FROM player
       NATURAL JOIN type
     ) AS T
GROUP BY year,
         type

帮助SQL查询加入？

4 个答案: