GOCREATE FUNCTION ExtStuff(@str NVARCHAR(MAX),@start INT,@len INT,@rep NVARCHAR(MAX))RETURNS NVARCHAR(MAX)ASBEGIN    DECLARE @rts NVARCHAR(MAX);    SELECT @rts=CASE WHEN @start>0 THEN STUFF(@str,@start,@len,@rep) WHEN @start<0 THEN REVERSE(STUFF(REVERSE(@str),-@start,@len,REVERSE(@rep))) ELSE NULL END;    RETURN @rts;END

例：

SELECT dbo.ExtStuff('123',3,1,'97')

//OUTPUT：

1297

SELECT dbo.ExtStuff('123',-1,1,'97')

//OUTPUT:

1297