SQL窗口函?一例

需求：

MSSQL，列出服 例中所有 的如下信息： ID、 名、 建日期、 文件 型、 文件大小、 大小、文件所在路 。

法(後面的百分比 所花 占比)：

-- 连接子查询  (47%)
WITH cte_TotalSize AS
(
	SELECT database_id
	      ,CAST(SUM(size) AS FLOAT)/128 AS [TotalSize(MB)]
	FROM sys.master_files
	GROUP BY database_id
)
SELECT a.database_id AS [DB_ID]
      ,b.name AS [DB_Name]
      ,b.create_date
      ,CASE a.type WHEN 1 THEN 'Log' ELSE 'Data' END AS File_Type
      ,CAST(a.size AS FLOAT)/128 AS [Size(MB)]  -- Size以页（8 KB）为单位
      ,c.[TotalSize(MB)]
      ,a.physical_Name AS File_Path
FROM sys.master_files a
INNER JOIN sys.databases b ON a.database_id = b.database_id
INNER JOIN cte_TotalSize c ON a.database_id = c.database_id


-- 标题子查询  (34%)
SELECT a.database_id AS [DB_ID]
      ,b.name AS [DB_Name]
      ,b.create_date
      ,CASE a.type WHEN 1 THEN 'Log' ELSE 'Data' END AS File_Type
      ,CAST(a.size AS FLOAT)/128 AS [Size(MB)]  -- Size以页（8 KB）为单位
      ,(SELECT CAST(SUM(size) AS FLOAT)/128 FROM sys.master_files WHERE database_id = a.database_id) AS [TotalSize(MB)]
      ,a.physical_Name AS File_Path 
FROM sys.master_files a
INNER JOIN sys.databases b ON a.database_id = b.database_id


-- 窗口函数  (19%)
SELECT a.database_id AS [DB_ID]
      ,b.name AS [DB_Name]
      ,b.create_date
      ,CASE a.type WHEN 1 THEN 'Log' ELSE 'Data' END AS File_Type
      ,CAST(a.size AS FLOAT)/128 AS [Size(MB)]  -- Size以页（8 KB）为单位
      ,CAST(SUM(size) OVER(PARTITION BY a.database_id) AS FLOAT)/128 AS [TotalSize(MB)]
      ,a.physical_Name AS File_Path 
FROM sys.master_files a
INNER JOIN sys.databases b ON a.database_id = b.database_id

果：

其中第三 是使用了窗口函 ，相 文 ：http://msdn.microsoft.com/zh-cn/library/ms189461.aspx