从一个serialize过的array的字符串中取出中取对应KEY的value

delimiter $$

create function get_from_serialized_json 
( in_string varchar(255), 
  in_key varchar(255) )
  returns varchar(255)
BEGIN
return trim( '"' from 
   substring_index(
    substring_index(
        substring(trim("}" FROM in_string ), locate(concat("\"",in_key,"\""), in_string  )+1 
    ) , ";",2 
   ), ":",-1 )) ;
END$$