讲解SQL Server数据库中函数的使用方法

◆1. 由于update里不能用存储过程，并且由于根据更新表的某些字段还要进行计算。所以很多人采用的是游标的方法，在这里我们可以用函数的方法实现。

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SQL Server 2000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