相关系数函数

[三碗猪脚]

对于SQL我还不会写自定义函数

求大侠帮写一个计算相关系数的函数

[dawugui]

函数的几种写法如下,至于你说的相关系数,就不清楚了.

A. 计算 ISO 周的标量值用户定义函数
下例中，用户定义函数 ISOweek 取日期参数并计算 ISO 周数。为了正确计算该函数，必须在调用该函数前唤醒调用 SET DATEFIRST 1。 

CREATE FUNCTION ISOweek  (@DATE datetime)
RETURNS int
AS
BEGIN
   DECLARE @ISOweek int
   SET @ISOweek= DATEPART(wk,@DATE)+1
      -DATEPART(wk,CAST(DATEPART(yy,@DATE) as CHAR(4))+'0104')
--Special cases: Jan 1-3 may belong to the previous year
   IF (@ISOweek=0) 
      SET @ISOweek=dbo.ISOweek(CAST(DATEPART(yy,@DATE)-1 
         AS CHAR(4))+'12'+ CAST(24+DATEPART(DAY,@DATE) AS CHAR(2)))+1
--Special case: Dec 29-31 may belong to the next year
   IF ((DATEPART(mm,@DATE)=12) AND 
      ((DATEPART(dd,@DATE)-DATEPART(dw,@DATE))>= 28))
      SET @ISOweek=1
   RETURN(@ISOweek)
END

下面是函数调用。注意 DATEFIRST 设置为 1。

SET DATEFIRST 1
SELECT master.dbo.ISOweek('12/26/1999') AS 'ISO Week'
下面是结果集。

ISO Week
----------------
52

B. 内嵌表值函数
下例返回内嵌表值函数。

USE pubs
GO
CREATE FUNCTION SalesByStore (@storeid varchar(30))
RETURNS TABLE
AS
RETURN (SELECT title, qty
      FROM sales s, titles t
      WHERE s.stor_id = @storeid and
      t.title_id = s.title_id)

C. 多语句表值函数
假设有一个表代表如下的层次关系： 

CREATE TABLE employees (empid nchar(5) PRIMARY KEY, 
      empname nvarchar(50), 
      mgrid nchar(5) REFERENCES employees(empid), 
      title nvarchar(30)
      )

表值函数 fn_FindReports(InEmpID) 有一个给定的职员ID，它返回与所有直接或间接向给定职员报告的职员相对应的表。该逻辑无法在单个查询中表现出来，不过可以实现为用户定义函数。 

CREATE FUNCTION fn_FindReports (@InEmpId nchar(5))
RETURNS @retFindReports TABLE (empid nchar(5) primary key,
   empname nvarchar(50) NOT NULL,
   mgrid nchar(5),
   title nvarchar(30))
/*Returns a result set that lists all the employees who report to given 
employee directly or indirectly.*/
AS
BEGIN
   DECLARE @RowsAdded int
   -- table variable to hold accumulated results
   DECLARE @reports TABLE (empid nchar(5) primary key, 
      empname nvarchar(50) NOT NULL,
      mgrid nchar(5),
      title nvarchar(30),
      processed tinyint default 0)
-- initialize @Reports with direct reports of the given employee 
   INSERT @reports
   SELECT empid, empname, mgrid, title, 0
   FROM employees 
   WHERE empid = @InEmpId 
   SET @RowsAdded = @@rowcount
   -- While new employees were added in the previous iteration
   WHILE @RowsAdded > 0
   BEGIN
      /*Mark all employee records whose direct reports are going to be 
   found in this iteration with processed=1.*/
      UPDATE @reports
      SET processed = 1
      WHERE processed = 0
      -- Insert employees who report to employees marked 1.
      INSERT @reports
      SELECT e.empid, e.empname, e.mgrid, e.title, 0
      FROM employees e, @reports r
      WHERE e.mgrid=r.empid and e.mgrid <> e.empid and r.processed = 1
      SET @RowsAdded = @@rowcount
      /*Mark all employee records whose direct reports have been found
   in this iteration.*/
      UPDATE @reports
      SET processed = 2
      WHERE processed = 1
   END
   
   -- copy to the result of the function the required columns
   INSERT @retFindReports
   SELECT empid, empname, mgrid, title 
   FROM @reports
   RETURN
END
GO

-- Example invocation
SELECT * 
FROM fn_FindReports('11234')
GO

[--小F--]

请楼主给出计算公式

[--小F--]

--各种字符串分函数

if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[f_splitSTR]') and xtype in (N'FN', N'IF', N'TF'))
drop function [dbo].[f_splitSTR]
GO

--3.2.1 循环截取法
CREATE FUNCTION f_splitSTR(
@s   varchar(8000),   --待分拆的字符串
@split varchar(10)     --数据分隔符
)RETURNS @re TABLE(col varchar(100))
AS
BEGIN
    DECLARE @splitlen int
    SET @splitlen=LEN(@split+'a')-2
    WHILE CHARINDEX(@split,@s)>0
    BEGIN
        INSERT @re VALUES(LEFT(@s,CHARINDEX(@split,@s)-1))
        SET @s=STUFF(@s,1,CHARINDEX(@split,@s)+@splitlen,'')
    END
    INSERT @re VALUES(@s)
    RETURN
END
GO

[huangqing_80]

相关系数，请楼主简单解释一下

[三碗猪脚]

http://baike.baidu.com/view/172091.htm

[icelovey]

我是来学习相关系数的

[sgtzzc]

相关系数是用以反映变量之间相关关系密切程度的统计指标。
相关系数是按积差方法计算，同样以两变量与各自平均值的离差为基础，通过两个离差相乘来反映两变量之间相关程度；着重研究线性的单相关系数。

有点难度...

[david0927cs2006]

相关系数
不明白
太专业了

[三碗猪脚]

http://baike.baidu.com/view/172091.htm

[yinxx11]

学习了 谢谢