下面我有一个简单的查询来获得今天加入"事件"表和"电影"表的所有电影评分。
Select e.*, m.moviename
From Event e, movie m
Where e.eventdate >= DATEADD(day, -1, GETDATE())
and e.moviekey = m.moviekey
order by e.Ratings desc;
问题
在上面的示例中,您将如何从1周前(1个月前)检索评分。因此,查询将返回2个额外的列CratingoneMonthago,RatingsOneWeekago等。
我研究了子征服,它没有单击任何帮助。
谢谢
您可以使用ctes将此信息提取(类似于使用子查询)。
以下查询假设您每天都有评分,并且没有重复(同一天的同一电影的多个评分):
WITH cteOneWeekAgo
AS
(
SELECT
moviekey
, Ratings
FROM Event
WHERE CAST(eventdate AS date) = DATEADD(WEEK, -1, CAST(GETDATE() AS date))
)
,
cteOneMonthAgo
AS
(
SELECT
moviekey
, Ratings
FROM Event
WHERE CAST(eventdate AS date) = DATEADD(MONTH, -1, CAST(GETDATE() AS date))
)
SELECT
e.*
, m.moviename
, w.Ratings Ratings_OneWeekAgo
, mth.Ratings Ratings_OneMonthAgo
FROM
Event e
JOIN movie m ON e.moviekey = m.moviekey
LEFT JOIN cteOneWeekAgo w ON e.moviekey = w.moviekey
LEFT JOIN cteOneMonthAgo mth ON e.moviekey = mth.moviekey
WHERE e.eventdate >= DATEADD(DAY, -1, GETDATE())
ORDER BY e.Ratings DESC
我还写了一个更复杂的查询,如果不存在该日期的评分,它将在您寻找的日期之前吸引电影的最新评分。
WITH cteOneWeekAgo
AS
(
SELECT
moviekey
, Ratings
, eventdate
FROM
(
SELECT
moviekey
, Ratings
, eventdate
, ROW_NUMBER() OVER (PARTITION BY moviekey ORDER BY eventdate DESC) R
FROM Event
WHERE CAST(eventdate AS date) <= DATEADD(WEEK, -1, CAST(GETDATE() AS date))
) Q
WHERE R = 1
)
,
cteOneMonthAgo
AS
(
SELECT
moviekey
, Ratings
, eventdate
FROM
(
SELECT
moviekey
, Ratings
, eventdate
, ROW_NUMBER() OVER (PARTITION BY moviekey ORDER BY eventdate DESC) R
FROM Event
WHERE CAST(eventdate AS date) <= DATEADD(MONTH, -1, CAST(GETDATE() AS date))
) Q
WHERE R = 1
)
SELECT
e.*
, m.moviename
, w.eventdate Ratings_OneWeekAgo_MostRecentDate
, w.Ratings Ratings_OneWeekAgo
, mth.eventdate Ratings_OneMonthAgo_MostRecentDate
, mth.Ratings Ratings_OneMonthAgo
FROM
Event e
JOIN movie m ON e.moviekey = m.moviekey
LEFT JOIN cteOneWeekAgo w ON e.moviekey = w.moviekey
LEFT JOIN cteOneMonthAgo mth ON e.moviekey = mth.moviekey
WHERE e.eventdate >= DATEADD(DAY, -1, GETDATE())
ORDER BY e.Ratings DESC