SELECT
REPLACE(
  REPLACE(
    REPLACE(
      REPLACE(
        REPLACE(
          REPLACE('6.87 "\s" "\s" 9 "\s" 8 "\s" "\s" "\s" "\s" 9.65','"\s"',' ')
        ,'  ',' ') 
      ,'  ',' ')
    ,'  ',' ')
  ,'  ',' ')
,' ',',');

 --- Получим  6.87,9,8,9.65 
 

REPLACE(str,from_str,to_str) 
Returns the string str with all all occurrences of the string from_str replaced by the string to_str: 
mysql> SELECT REPLACE('www.mysql.com', 'w', 'Ww');
        -> 'WwWwWw.mysql.com'

This function is multi-byte safe.