create table Readers (
reader_id number PRIMARY KEY,
r_ticket_num number ,
open_date date,
person_id number
);
/
ALTER TABLE Readers ADD CONSTRAINT Readers_FK1 FOREIGN KEY (person_id)
	  REFERENCES  Persons (pers_id) ENABLE
/
create table Persons (
pers_id number PRIMARY KEY,
fio varchar2( 100 ) ,
type_id number
);
/
ALTER TABLE Persons ADD CONSTRAINT Persons_FK1 FOREIGN KEY (type_id)
	  REFERENCES  Pers_type (type_id) ENABLE
/
create table Pers_type (
type_id number PRIMARY KEY,
type_name varchar2( 100 ) 
);
/