SQL Server里函数的两种用法（可以代替游标）
1． 因为update里不能用存储过程，然而要根据更新表的某些字段还要进行计算。我们常常采用游标的方法，这里用函数的方法实现。

函数部分：
CREATE FUNCTION [DBO].[FUN_GETTIME] (@TASKPHASEID INT)
RETURNS FLOAT AS
BEGIN
  DECLARE @TASKID INT,
          @HOUR FLOAT,
          @PERCENT FLOAT,
          @RETURN FLOAT
  IF @TASKPHASEID IS NULL
  BEGIN
    RETURN(0.0)
  END

SELECT @TASKID=TASKID,@PERCENT=ISNULL(WORKPERCENT,0)/100
FROM TABLETASKPHASE
WHERE ID=@TASKPHASEID

SELECT @HOUR=ISNULL(TASKTIME,0) FROM TABLETASK
WHERE ID=@TASKID

SET @RETURN=@HOUR*@PERCENT
RETURN (@RETURN)
END

调用函数的存储过程部分
CREATE PROCEDURE [DBO].[PROC_CALCCA]
@ROID INT
  AS
BEGIN
  DECLARE @CA FLOAT

  UPDATE TABLEFMECA
  SET
  Cvalue_M=    ISNULL(MODERATE,0)*ISNULL(FMERATE,0)*ISNULL(B.BASFAILURERATE,0)*[DBO].[FUN_GETTIME](C.ID)
FROM TABLEFMECA ,TABLERELATION B,TABLETASKPHASE C
WHERE ROID=@ROID AND TASKPHASEID=C.ID AND B.ID=@ROID

  SELECT @CA=SUM(ISNULL(Cvalue_M,0)) FROM TABLEFMECA WHERE ROID=@ROID

UPDATE TABLERELATION
  SET CRITICALITY=@CA
  WHERE ID=@ROID
END
GO

2． 我们要根据某表的某些记录，先计算后求和，因为无法存储中间值，平时我们也用游标的方法进行计算。但sqlserver2000里支持
SUM ( [ ALL | DISTINCT ] expression )

expression

是常量、列或函数，或者是算术、按位与字符串等运算符的任意组合。因此我们可以利用这一功能。

函数部分：

CREATE FUNCTION [DBO].[FUN_RATE] (@PARTID INT,@ENID INT,@SOURCEID INT, @QUALITYID INT,@COUNT INT)

RETURNS FLOAT AS
BEGIN
  DECLARE @QXS FLOAT, @G FLOAT, @RATE FLOAT

  IF (@ENID=NULL) OR (@PARTID=NULL) OR (@SOURCEID=NULL) OR (@QUALITYID=NULL)
  BEGIN
    RETURN(0.0)
  END

  SELECT @QXS= ISNULL(XS,0) FROM TABLEQUALITY WHERE ID=@QUALITYID
  SELECT @G=ISNULL(FRATE_G,0) FROM TABLEFAILURERATE
  WHERE (SUBKINDID=@PARTID) AND( ENID=@ENID) AND ( DATASOURCEID=@SOURCEID) AND( ( (ISNULL(MINCOUNT,0)<=ISNULL(@COUNT,0)) AND ( ISNULL(MAXCOUNT,0)>=ISNULL(@COUNT,0)))
OR(ISNULL(@COUNT,0)>ISNULL(MAXCOUNT,0)))

  SET @RATE=ISNULL(@QXS*@G,0)
  RETURN (@RATE)
END

调用函数的存储过程部分：

CREATE PROC PROC_FAULTRATE

@PARTID INTEGER, @QUALITYID INTEGER, @SOURCEID INTEGER, @COUNT INTEGER, @ROID INT, @GRADE INT,@RATE FLOAT=0 OUTPUTAS
BEGIN
  DECLARE
    @TASKID INT
    SET @RATE=0.0

SELECT @TASKID=ISNULL(TASKPROID,-1) FROM TABLERELATION WHERE ID=(SELECT PID FROM TABLERELATION WHERE ID=@ROID)

    IF (@TASKID=-1) OR(@GRADE=1) BEGIN
       SET @RATE=0
    RETURN
END

    SELECT @RATE=SUM([DBO].[FUN_RATE] (@PARTID,ENID,@SOURCEID, @QUALITYID,@COUNT) *ISNULL(WORKPERCENT,0)/100.0)

    FROM TABLETASKPHASE
    WHERE TASKID=@TASKID
END
GO

函数还可以返回表等，希望大家一起讨论sqlserver里函数的妙用。