生成编码规则调整处理T-SQL语句的函数

CREATE FUNCTION dbo.f_ChangeCodeRule(
@Old_CodeRule varchar(50), --以逗号分隔的旧的编码规则,每层编码的长度,比如1,2,3,表示有三层编码,第一层长度为1,第二层长度为2,第三层长度为3
@New_CodeRule varchar(50), --以逗号分隔的旧的编码规则,如果某个层次的编码长度为0,表示删除该层编码
@CharFill char(1), --扩充编码时,填充的字符
@Position int, --为0,从编码的最前面开始压缩或者填充,为-1或者大于旧编码的长度,从最后一位开始处理,为其他值,从指定的位置后开始处理
@FieldName sysname --编码字段名
)RETURNS nvarchar(4000)
AS
BEGIN
IF ISNULL(@CharFill,'')='' SET @CharFill=N'0'
DECLARE @old_Code TABLE(ID int IDENTITY,CodeLen int,CodeLens int,Code nvarchar(200))
DECLARE @new_Code TABLE(ID int IDENTITY,CodeLen int)
--插分旧编码规则到表
DECLARE @CodeLen varchar(10),@CodeLens varchar(10)
SET @CodeLens=1
WHILE CHARINDEX(N',',@Old_CodeRule)>0
BEGIN
SELECT @CodeLen=LEFT(@Old_CodeRule,CHARINDEX(N',',@Old_CodeRule)-1),
@Old_CodeRule=STUFF(@Old_CodeRule,1,CHARINDEX(N',',@Old_CodeRule),N'')
INSERT @old_Code VALUES(@CodeLen,@CodeLens,N'SUBSTRING('+@FieldName+N','+@CodeLens+N','+@CodeLen+N')')
SET @CodeLens=@CodeLens+CAST(@CodeLen as int)
END
INSERT @old_Code VALUES(@Old_CodeRule,@CodeLens,N'SUBSTRING('+@FieldName+N','+@CodeLens+N','+@Old_CodeRule+N')')

--插分新编码规则到表
WHILE CHARINDEX(N',',@New_CodeRule)>0
BEGIN
INSERT @new_Code VALUES(LEFT(@New_CodeRule,CHARINDEX(N',',@New_CodeRule)-1))
SET @New_CodeRule=STUFF(@New_CodeRule,1,CHARINDEX(N',',@New_CodeRule),N'')
END
INSERT @new_Code VALUES(@New_CodeRule)

--生成编号规则修改处理语句
DECLARE @sql nvarchar(4000)
SET @sql=''
SELECT @sql=@sql
+CASE
WHEN n.CodeLen=0 THEN '' --新编码长度为0,表示去掉这段编码
ELSE N'+CASE WHEN LEN('+@FieldName
+N')<'+CAST(o.CodeLens as varchar)
+N' THEN '''' ELSE '+CASE
WHEN n.CodeLen=o.CodeLen THEN N'+'+o.Code --新旧编码长度相同时不需要处理
WHEN n.CodeLen>o.CodeLen THEN CASE --扩充编码长度的处理,根据@Position和旧编码长度决定编码的填充位置
WHEN @Position=-1 OR @Position>=o.CodeLen
THEN N'+'+o.Code
+N'+'+QUOTENAME(REPLICATE(@CharFill,n.CodeLen-o.CodeLen),N'''')
ELSE N'+STUFF('+o.Code
+N','+CAST(@Position+1 as varchar)
+N',0,'+QUOTENAME(REPLICATE(@CharFill,n.CodeLen-o.CodeLen),N'''')
+N')'
END
ELSE CASE --收缩编码长度的处理,根据@Position和新编码长度决定编码的截取位置
WHEN @Position=-1 OR @Position>n.CodeLen
THEN '+LEFT('+o.Code+N','+CAST(n.CodeLen as varchar)+N')'
ELSE N'+STUFF('+o.Code
+N','+CAST(@Position+1 as varchar)
+N','+CAST(o.CodeLen-n.CodeLen as varchar)
+N','''')'
END
END
+N' END'
END
FROM @old_Code o,@new_Code n
WHERE o.ID=n.ID
RETURN(STUFF(@sql,1,1,N''))
END