golang gorm关系关联
Jeff的技术栈 人气:01. 关联
1.1. 属于
// `User`属于`Profile`, `ProfileID`为外键 type User struct { gorm.Model Profile Profile ProfileID int } type Profile struct { gorm.Model Name string } db.Model(&user).Related(&profile) //// SELECT * FROM profiles WHERE id = 111; // 111是user的外键ProfileID
指定外键
type Profile struct { gorm.Model Name string } type User struct { gorm.Model Profile Profile `gorm:"ForeignKey:ProfileRefer"` // 使用ProfileRefer作为外键 ProfileRefer int }
指定外键和关联外键
type Profile struct { gorm.Model Refer string Name string } type User struct { gorm.Model Profile Profile `gorm:"ForeignKey:ProfileID;AssociationForeignKey:Refer"` ProfileID int }
1.2. 包含一个
// User 包含一个 CreditCard, UserID 为外键 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的字段名称,这意味着获得user的CreditCard关系并将其填充到变量 // 如果字段名与变量的类型名相同,如上例所示,可以省略,如: db.Model(&user).Related(&card)
指定外键
type Profile struct { gorm.Model Name string UserRefer uint } type User struct { gorm.Model Profile Profile `gorm:"ForeignKey:UserRefer"` }
指定外键和关联外键
type Profile struct { gorm.Model Name string UserID uint } type User struct { gorm.Model Refer string Profile Profile `gorm:"ForeignKey:UserID;AssociationForeignKey:Refer"` }
1.3. 包含多个
// User 包含多个 emails, UserID 为外键 type User struct { gorm.Model Emails []Email } type Email struct { gorm.Model Email string UserID uint } db.Model(&user).Related(&emails) //// SELECT * FROM emails WHERE user_id = 111; // 111 是 user 的主键
指定外键
type Profile struct { gorm.Model Name string UserRefer uint } type User struct { gorm.Model Profiles []Profile `gorm:"ForeignKey:UserRefer"` }
指定外键和关联外键
type Profile struct { gorm.Model Name string UserID uint } type User struct { gorm.Model Refer string Profiles []Profile `gorm:"ForeignKey:UserID;AssociationForeignKey:Refer"` }
1.4. 多对多
// User 包含并属于多个 languages, 使用 `user_languages` 表连接 type User struct { gorm.Model Languages []Language `gorm:"many2many:user_languages;"` } type Language struct { gorm.Model Name string } db.Model(&user).Related(&languages, "Languages") //// SELECT * FROM "languages" INNER JOIN "user_languages" ON "user_languages"."language_id" = "languages"."id" WHERE "user_languages"."user_id" = 111
指定外键和关联外键
type CustomizePerson struct { IdPerson string `gorm:"primary_key:true"` Accounts []CustomizeAccount `gorm:"many2many:PersonAccount;ForeignKey:IdPerson;AssociationForeignKey:IdAccount"` } type CustomizeAccount struct { IdAccount string `gorm:"primary_key:true"` Name string }
译者注:这里设置好像缺失一部分
1.5. 多种包含
支持多种的包含一个和包含多个的关联
type Cat struct { Id int Name string Toy Toy `gorm:"polymorphic:Owner;"` } type Dog struct { Id int Name string Toy Toy `gorm:"polymorphic:Owner;"` } type Toy struct { Id int Name string OwnerId int OwnerType string }
注意:多态属性和多对多显式不支持,并且会抛出错误。
1.6. 关联模式
关联模式包含一些帮助方法来处理关系事情很容易。
// 开始关联模式 var user User db.Model(&user).Association("Languages") // `user`是源,它需要是一个有效的记录(包含主键) // `Languages`是关系中源的字段名。 // 如果这些条件不匹配,将返回一个错误,检查它: // db.Model(&user).Association("Languages").Error // Query - 查找所有相关关联 db.Model(&user).Association("Languages").Find(&languages) // Append - 添加新的many2many, has_many关联, 会替换掉当前 has_one, belongs_to关联 db.Model(&user).Association("Languages").Append([]Language{languageZH, languageEN}) db.Model(&user).Association("Languages").Append(Language{Name: "DE"}) // Delete - 删除源和传递的参数之间的关系,不会删除这些参数 db.Model(&user).Association("Languages").Delete([]Language{languageZH, languageEN}) db.Model(&user).Association("Languages").Delete(languageZH, languageEN) // Replace - 使用新的关联替换当前关联 db.Model(&user).Association("Languages").Replace([]Language{languageZH, languageEN}) db.Model(&user).Association("Languages").Replace(Language{Name: "DE"}, languageEN) // Count - 返回当前关联的计数 db.Model(&user).Association("Languages").Count() // Clear - 删除源和当前关联之间的关系,不会删除这些关联 db.Model(&user).Association("Languages").Clear()
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