drop table if exists c;
drop table if exists b;
drop table if exists a;
create table a (
    pa varchar(70) primary key
)
   engine InnoDB
  charset ascii
;

create table b (
    bid int auto_increment primary key,
    pa varchar(70),
    rt varchar(70) default NULL,
    foreign key fka_b (pa) references a (pa)
        on delete cascade
)
   engine InnoDB
  charset ascii
;

create table c (
    cid int auto_increment primary key,
    pa varchar(70),
    a varchar(2000), 
    i varchar(2000), 
    t varchar(300), 
    foreign key fka_c (pa) references a (pa)
        on delete cascade
)
   engine InnoDB
  charset ascii
;