Mapping one-to-one relationship

Question

Hi mates, i have two tables
// Car Table CREATE TABLE CAR ( CAR_ID NUMBER(19,0) DEFAULT 1 NOT NULL, LAST_UPDATE TIMESTAMP DEFAULT SYSDATE, MAKE VARCHAR2(20), MODEL NUMBER(5,0), REGISTRATION VARCHAR2(25), MILEAGE NUMBER, ENGINE_SIZE NUMBER(1,1), TANK_SIZE NUMBER(2,0), GAS_IN_TANK NUMBER(2,0), CATEGORY_ID NUMBER(19,0) DEFAULT 1 NOT NULL, PRIMARY KEY (CAR_ID) ); // Contract CREATE TABLE CONTRACT ( CONTRACT_ID NUMBER(19,0) DEFAULT 1 NOT NULL, LAST_UPDATE DATE DEFAULT SYSDATE, STATUS VARCHAR2(32), ORDER_NUMBER VARCHAR2(32), RENTAL_DATE DATE, CUSTOMER_ID NUMBER(19,0) DEFAULT 1 NOT NULL, PRIMARY KEY (CONTRACT_ID) );
I need to establish a one-to-one relationship here (a contract has one car associated to it, car will only belong to one active contract ) .. If i add foreign key to Car and reference Contract
ALTER TABLE CAR ADD FOREIGN KEY (CAR_ID) REFERENCES CONTRACT (CONTRACT_ID) ;
Then use reverse engineering to create hibernate mappings (in eclipse), i get a one-to-many relationship (contract has many cars)? how do i enforce table to to be interpreted this way?

Answer 1

sonx wrote:
(a contract has one car associated to it, car will only belong to one active contract ) The relationship is from contract to car.
.. If i add foreign key to Car and reference Contract
ALTER TABLE CAR
     ADD FOREIGN KEY (CAR_ID)
     REFERENCES CONTRACT (CONTRACT_ID)
;This relationship is from car to contract.
Which contradicts what you said above.
And isn't logical. A car will over time belong to different contracts. Each contract retains the original car. The car can't contain all of them.