alter table student_tbl drop constraint FK_STUDENT_PERSON_TBL;alter table employee_tbl drop constraint FK_EMPLOYEE_PERSON_TBL;alter table resume_tbl drop constraint FK_RESUME_EMPLOYEE_TBL;alter table student_tbl drop constraint PK_STUDENT_TBL;alter table employee_tbl drop constraint PK_EMPLOYEE_TBL;alter table resume_tbl drop constraint PK_RESUME_TBL;alter table person_tbl drop constraint PK_PERSON_TBL;drop table person_tbl cascade constraint;drop table student_tbl cascade constraint;drop table employee_tbl cascade constraint;drop table resume_tbl cascade constraint;create table person_tbl (    id  varchar2(20) not null,    firstname varchar2(20) not null,    lastname varchar2(20) not null,    address  varchar2(200),    constraint PK_PERSON_TBL primary key (id));create table student_tbl (    id varchar2(20) not null,    salutation varchar2(20) not null,    person_id varchar2(20) not null,    constraint PK_STUDENT_TBL primary key (id));create table employee_tbl (    id varchar2(20) not null,    SSN varchar2(20) not null,    person_id   varchar2(20) not null,    constraint PK_EMPLOYEE_TBL primary key (id));create table resume_tbl (    id  varchar2(20) not null,    startdate   date not null,    enddate     date,    description varchar2(200) not null,    employee_id varchar2(20),    constraint PK_RESUME_TBL primary key (id));alter table student_tbl add constraint FK_STUDENT_PERSON_TBL foreign key (person_id) referenceS person_tbl (id);alter table employee_tbl add constraint FK_EMPLOYEE_PERSON_TBL foreign key (person_id) referenceS person_tbl (id);alter table resume_tbl add constraint FK_RESUME_EMPLOYEE_TBL foreign key (employee_id) references employee_tbl (id);commit;