Count total number of char and their type in a string using sql server

//////////////// Sql String

declare @str varchar(max)='this is a test string', @tlen int=0,@lstStr varchar(max)='',@fStr varchar(max)='',@Fchar varchar(10)=''

set @tlen=len(@str)

while @tlen>0

begin

set @Fchar=left(@str,1)

set @fStr=@fStr+'Total Count of '''+@Fchar+''' :  '+cast(len(@str)-len(replace(@str,@Fchar,'')) as varchar)+', '

set @str=replace(@str,@Fchar,'')

set @tlen=len(@str)

end

print @fStr

///////////////////// Result

Total Count of 't' :  4, Total Count of 'h' :  1, Total Count of 'i' :  3, Total Count of 's' :  4, Total Count of ' ' :  4, Total Count of 'a' :  1, Total Count of 'e' :  1, Total Count of 'r' :  1, Total Count of 'n' :  1, Total Count of 'g' :  1,