sql计算(,1,2,3,4,)中有几个数目字

sql计算(,1,2,3,4,)中有几个数字
ALTER function [dbo].[数量](@str varchar(500))
returns int
as
begin
declare @n int
declare @m int
declare @i int
declare @jg char(20)
set @n=len(@str)
set @m=0
set @i=1
while @i<[email protected]
 begin
  set @jg=substring(@str,@i,1)
  if @jg=','
   set @[email protected]+1
  set @[email protected]+1
 end 
return @m-1
end