SQL>
SQL> create table gender_tab (
2 gender_id char(1),
3 gender_nm varchar2(6),
4 constraint gender_pk primary key (gender_id),
5 constraint gender_id_ck check (gender_id in ('M', 'F'))
6 );
Table created.
SQL>
SQL> insert into gender_tab values ('F', 'Female');
1 row created.
SQL> insert into gender_tab values ('M', 'Male');
1 row created.
SQL>
SQL> create table people (
2 first_name varchar2(20),
3 last_name varchar2(25),
4 gender char(1)
5 );
Table created.
SQL>
SQL> alter table people
2 add constraint people_gender_fk
3 foreign key (gender)
4 references gender_tab;
Table altered.
SQL>
SQL> insert into people values ('S', 'Dillon', 'M');
1 row created.
SQL> insert into people values ('C', 'Beck', 'M');
1 row created.
SQL> insert into people values ('N', 'Ellis', 'F');
1 row created.
SQL>
SQL> drop table gender_tab;
drop table gender_tab
*
ERROR at line 1:
ORA-02449: unique/primary keys in table referenced by foreign keys
SQL>
SQL> drop table gender_tab cascade constraints;
Table dropped.
SQL>
SQL>