分析SQL Server里函数的两种用法

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.大家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)))
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。