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[英]Same data, different results when using PARTITION BY and ROW_NUMBER
[英]Using Row Number to Partition data
好的,這是我斷定我迷路的情況之一。
我有一個看起來像這樣的表:
我寫了以下代碼:
WITH CTE AS(
SELECT
USER_NBR
,CASE WHEN MOVIE_TYPE = 'Action' THEN MOVIE_NAME END [ACTION]
,CASE WHEN MOVIE_TYPE = 'Drama' THEN MOVIE_NAME END DRAMA
,CASE WHEN MOVIE_TYPE = 'Romance' THEN MOVIE_NAME END ROMANCE
,ROW_NUMBER() OVER (PARTITION BY USER_NBR ORDER BY USER_NBR) AS OCCURANCE
FROM dbo.MOVIE)
SELECT * FROM CTE WHERE OCCURANCE = 1
我得到這個結果:
我不明白的是為什么查詢結果中會出現Nulls?
我究竟做錯了什么? 如您所見,我正在對電影進行分類。
感謝您簽出
也許這種方法對您有用。 通常,當您將行值轉換為列時(如示例中的影片類型),它是一個樞軸函數(請參閱http://msdn.microsoft.com/zh-cn/library/ms177410.aspx )
select * from
(select user_nbr, movie_name, movie_type from movies) as movies
pivot
(max(movie_name)
for movie_type in ([Action], [Drama], [Romance])
)
as PivotTable
結果:
user_nbr Action Drama Romance
101 Casino Royale Pretty Woman Love Actually
102 Casino Royale Pretty Woman Love Actually
請注意,如果您嘗試獲取此類輸出,則必須使用group by子句..
如果您想獲取所有類別的價值,則可以嘗試以下查詢..
WITH CTE AS(
SELECT
USER_NBR
,CASE WHEN MOVIE_TYPE = 'Action' THEN MOVIE_NAME END [ACTION]
,CASE WHEN MOVIE_TYPE = 'Drama' THEN MOVIE_NAME END DRAMA
,CASE WHEN MOVIE_TYPE = 'Romance' THEN MOVIE_NAME END ROMANCE
,count(*) AS OCCURANCE
FROM dbo.MOVIE
group by USER_NBR
)
SELECT * FROM CTE
我想這就是你想要做的..
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