sql sever string interception of Chinese characters

Recently, I need to intercept Chinese characters from SQL strings, use the unicode function to determine the unicode encoding of the characters, and filter out non-Chinese characters according to the encoding range.

Written as a function

/*@str Need to get the string of Chinese characters*/

create function CharRep(@str nvarchar(200))
returns nvarchar(200)
as 
begin 
 declare @i int, @char nvarchar(1), @zh nvarchar(200)
 set @i = 1
 set @zh = ''
 while @i <= len(@str)
 begin
  set @char = substring(@str, @i, 1)
  if  unicode(@char) between 19968 And 40869
   set @zh = @zh + @char
  set @i = @i + 1
 end
 return @zh
end

Execute select dbo.CharRep('Nonghao a/bc Nonghao')

The result a/bc

Attached:

unicode encoding range:
Chinese characters: [0x4e00,0x9fa5] (or decimal [19968, 40869])
Numbers: [0x30, 0x39] (or decimal [48, 57]) Search
lowercase letters: [0x61, 0x7a] (or decimal [97, 122])
Capital letters: [0x41,0x5a] (or decimal [65, 90])