How to remove last character of a string(mysql Query fields)?

SELECT Concat( mid( fieldname, 1, length(fieldname) -1 )

 , REPLACE( mid(fieldname, length(fieldname) ) , ',', "" ) )

 as fieldname FROM tablename

OR

Select id, REPLACE(fieldname,',','') from tablename 

where fieldname REGEXP '(.*),' limit 5;

UPDATE tablename SET fieldname = Concat( mid(fieldname,

 1, length(fieldname) -1 ) , REPLACE( mid(fieldname, 

length(fieldname) ) , ',', "" ) )