sql server function to mysql with same logic -

the below sql server function converted mysql in mysql substring working in different manner when compared sql server can make execute in mysql same logic?

alter function [dbo].[udf_num_towords] (  @number numeric (38, 0) -- input number many 18 digits  ) returns varchar(8000)    begin     declare @inputnumber varchar(38)  declare @numberstable table (number char(2), word varchar(10))   declare @outputstring varchar(8000)  declare @length int  declare @counter int declare @loops int  declare @position int declare @chunk char(3) -- chunks of 3 numbers declare @tensones char(2) declare @hundreds char(1) declare @tens char(1) declare @ones char(1)  if @number = 0 return 'zero'  -- initialize variables select @inputnumber = convert(varchar(38), @number)  , @outputstring = ''  , @counter = 1 select @length   = len(@inputnumber)  , @position = len(@inputnumber) - 2  , @loops    = len(@inputnumber)/3  -- make sure there loop added remaining numbers if len(@inputnumber) % 3 <> 0 set @loops = @loops + 1   -- insert data numbers , words  insert @numberstable   select '00', '' union select '01', 'one' union select '02', 'two' union select '03', 'three' union select '04', 'four' union select '05', 'five'  union select '06', 'six' union select '07', 'seven' union select '08', 'eight' union select '09', 'nine'  union select '10', 'ten' union select '11', 'eleven'union select '12', 'twelve' union select '13', 'thirteen'union select '14', 'fourteen' union select '15', 'fifteen' union select '16', 'sixteen' union select '17', 'seventeen'union select '18', 'eighteen' union select '19', 'nineteen'union select '20', 'twenty' union select '30', 'thirty'  union select '40', 'forty' union select '50', 'fifty'   union select '60', 'sixty' union select '70', 'seventy' union select '80', 'eighty' union select '90', 'ninety'     while @counter <= @loops begin  -- chunks of 3 numbers @ time, padded leading zeros set @chunk = right('000' + substring(@inputnumber, @position, 3), 3)  if @chunk <> '000' begin     select @tensones = substring(@chunk, 2, 2)          , @hundreds = substring(@chunk, 1, 1)          , @tens = substring(@chunk, 2, 1)          , @ones = substring(@chunk, 3, 1)      -- if twenty or less, use word directly @numberstable     if convert(int, @tensones) <= 20 or @ones='0' begin         set @outputstring = (select word                                    @numberstable                                    @tensones = number)                + case @counter when 1 '' -- no name                    when 2 ' thousand ' when 3 ' million '                    when 4 ' billion '  when 5 ' trillion '                    when 6 ' quadrillion ' when 7 ' quintillion '                    when 8 ' sextillion '  when 9 ' septillion '                    when 10 ' octillion '  when 11 ' nonillion '                    when 12 ' decillion '  when 13 ' undecillion '                    else '' end                            + @outputstring         end      else begin -- break down ones , tens separately           set @outputstring = ' '                          + (select word                                  @numberstable                                  @tens + '0' = number)                          + '-'                          + (select word                                  @numberstable                                  '0'+ @ones = number)                + case @counter when 1 '' -- no name                    when 2 ' thousand ' when 3 ' million '                    when 4 ' billion '  when 5 ' trillion '                    when 6 ' quadrillion ' when 7 ' quintillion '                    when 8 ' sextillion '  when 9 ' septillion '                    when 10 ' octillion '  when 11 ' nonillion '                    when 12 ' decillion '   when 13 ' undecillion '                    else '' end                         + @outputstring     end      -- hundreds     if @hundreds <> '0' begin         set @outputstring  = (select word                                    @numberstable                                    '0' + @hundreds = number)                             + ' hundred '                              + @outputstring     end end  select @counter = @counter + 1      , @position = @position - 3     end     -- remove double spaces    set @outputstring = ltrim(rtrim(replace(@outputstring, '  ', ' ')))    set @outputstring = upper(left(@outputstring, 1)) +     substring(@outputstring, 2,    8000)       return @outputstring -- return result    end