> 本章介紹一對一關系（has one） [TOC] ## 一對一關系（has one） ~~~ // User 包含一個 CreditCard, UserID 為外鍵 type User struct { gorm.Model CreditCard CreditCard } type CreditCard struct { gorm.Model UserID uint Number string } var card CreditCard db.Model(&user).Related(&card, "CreditCard") //// SELECT * FROM credit_cards WHERE user_id = 123; // 123 is user's primary key // CreditCard是user的字段名稱，這意味著獲得user的CreditCard關系并將其填充到變量 // 如果字段名與變量的類型名相同，如上例所示，可以省略，如： db.Model(&user).Related(&card) ~~~ ## 指定外鍵 ~~~ type Profile struct { gorm.Model Name string UserRefer uint } type User struct { gorm.Model Profile Profile `gorm:"ForeignKey:UserRefer"` } ~~~ ## 指定外鍵和關聯外鍵 ~~~ type Profile struct { gorm.Model Name string UserID uint } type User struct { gorm.Model Refer string Profile Profile `gorm:"ForeignKey:UserID;AssociationForeignKey:Refer"` } ~~~