Question

如标题所述，我想选择每个团队和每年的活动数量。下面的选择声明工作正常，但不能完全满足我的要求。

SELECT
 Team.team_id,
 TO_CHAR(Event.START_DATE_TIME, 'yyyy') AS year,
 count(event_id)    AS events
FROM
 Team
LEFT OUTER JOIN
 Event ON Event.team_id = Team.team_id
GROUP BY
 TO_CHAR(Event.START_DATE_TIME, 'yyyy'),
 team_id
ORDER BY
 year  ASC,
 team_id  ASC
;

有了这个，如果我们有：

Team 1 : 1 event in 2006
Team 2 : 1 event in 2007

我们获得：

ID | Year | Events
------------------
1  | 2006 | 1
2  | 2007 | 1

我想获得：

ID | Year | Events
-------------------
1  | 2006 | 1
2  | 2006 | 0
1  | 2007 | 0
2  | 2007 | 1

我不知道如何修改我的请求。

Answer 1

使用：

   SELECT x.team_id,
          x.year,
          COALESCE(COUNT(e.event_id), 0) AS events
     FROM (SELECT :start_year + LEVEL - 1 AS year,
                  t.team_id
             FROM DUAL, TEAM t
       CONNECT BY :start_year + LEVEL - 1 <= :end_year) x
LEFT JOIN EVENT e ON EXTRACT(YEAR FROM e.start_date_time) = x.year
                 AND e.team_id = x.team_id

这将生成一个年份列表，但您必须设置:start_year和:end_year BIND变量。

此前：

   SELECT x.team_id,
          x.year,
          COALESCE(COUNT(e.event_id), 0) AS events
     FROM (SELECT 2006 AS year,
                  a.team_id
             FROM TEAM a
           UNION ALL
           SELECT 2007,
                  b.team_id
             FROM TEAM b) x
LEFT JOIN EVENT e ON EXTRACT(YEAR FROM e.start_date_time) = x.year
                 AND e.team_id = x.team_id

TO_CHAR可以获得年份，但是将其作为CHAR（4）返回，因此您需要使用TO_NUMBER(TO_CHAR(date_col, 'yyyy'))来获取数字。所以我使用了EXTRACT代替......

Answer 2

我这里没有Oracle进行测试，但总的来说这应该可行：

SELECT
 Team.team_id,
 Years.year,
 COALESCE(count(Event.event_id),0) events
FROM
 Team
   JOIN (SELECT DISTINCT EXTRACT(YEAR FROM start_date_time) year FROM Event) Years ON 1=1
   LEFT OUTER JOIN Event ON Event.team_id = Team.team_id AND EXTRACT(YEAR FROM Event.start_date_time) = Years.year
GROUP BY
 Years.year,
 team_id
ORDER BY
 year  ASC,
 team_id  ASC
;

您将获得每年的结果，您可以在活动中获得活动。如果这还不够，你可以用一个填满所有年份的表替换Years子。

Answer 3

所以它有效！ :) 这是我的最终查询：

SELECT
 Team.name,
 Years.year,
 count(Event.event_id)
FROM
    Team
JOIN
    (
        SELECT DISTINCT EXTRACT(YEAR FROM start_date_time) AS year
        FROM Event
    ) Years ON 1 = 1
LEFT OUTER JOIN
    Event ON    Event.team_id = Team.team_id
                AND EXTRACT(YEAR FROM Event.start_date_time) = Years.year
WHERE
    event_type = 'C'
GROUP BY
    Team.name,
    Years.year
ORDER BY
    Year ASC,
    name ASC
;

谢谢！

Oracle SELECT：每个团队和每年的事件数

3 个答案: