查找指定第几个字符窜所在的位置的SQL标量函数的制作方法

查找指定第几个字符窜所在的位置的SQL标量函数的制作方法
返回@find在@str中第(@n)次出现的位置。没有第(@n)次返回0

方法很多种，下面是其中的一种
create function fn_find(@find varchar(8000), @str varchar(8000), @n smallint)
returns int
as
begin
if @n < 1 return (0)
declare @start smallint, @count smallint, @index smallint, @len smallint
set @index = charindex(@find, @str)
if @index = 0 return (0)
else select @count = 1, @len = len(@find)
while @index > 0 and @count < @n
begin
set @start = @index + @len
select @index = charindex(@find, @str, @start), @count = @count + 1
end
if @count < @n set @index = 0
return (@index)
end
go
declare @str varchar(100)
set @str='A,B,C,D,A,B,C,D,C,D,B,A,C,E'
select dbo.fn_find('A',@str,1) as one, dbo.fn_find('A',@str,2) as two, dbo.fn_find('A',@str,3) as three, dbo.fn_find('A',@str,4) as four