User : 
	id number;
	name varchar(20);

Address :
	addr_name varchar(40);

第一種情況: 一對一關系

方法一:
CREATE TABLE user
( id NUMBER(2) CONSTRAINT user_id_pk PRIMARY KEY ,
  name VARCHAR(20) CONSTRAINT user_name_nl NOT NULL ,
  addr_name VARCHAR(40) CONSTRAINT addr_name_nl NOT NULL);

方法二:
CREATE TABLE user
( id NUMBER(2) CONSTRAINT user_id_pk PRIMARY KEY ,
  name VARCHAR(20) CONSTRAINT user_name_nl NOT NULL );

CREATE TABLE address
( addr_name VARCHAR(40) CONSTRAINT addr_name_nl NOT NULL,
  id NUMBER(2) CONSTRAINT user_id_fk REFERENCE user(id),
	       CONSTRAINT user_id_uq UNIQUE(addr_name,id));

第二種情況:一對多關系

CREATE TABLE user 
( id NUMBER(2) CONSTRAINT user_id_pk PRIMARY KEY ,
  name VARCHAR(20) CONSTRAINT user_name_nl NOT NULL );

CREATE TABLE address
( addr_id NUMBER(2) CONSTRAINT addr_id_pk PRIMARY KEY ,
  addr_name VARCHAR(20) CONSTRAINT addr_name_nl NOT NULL,
  id NUMBER(2) CONSTRAINT addr_id_fk FOREIGN KEY(id) REFERENCE user(id));

第三種情況:多對多關系

CREATE TABLE user 
( id NUMBER(2) CONSTRAINT user_id PRIMARY KEY ,
  name VARCHAR(20) CONSTRAINT user_name NOT NULL );

CREATE TABLE address
( addr_id NUMBER(2) CONSTRAINT addr_id_pk PRIMARY KEY,
  addr_name VARCHAR(40)CONSTRAINT addr_name_nl NOT NULL);

CREATE TABLE user_addr
( id NUMBER(2),
  addr_id NUMBER(2),
  CONSTRAINT user_addr_id_pk PRIMARY KEY(id,addr_id));