1. 关联
1.1. 属于
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// `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
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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
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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
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// 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 CreditCarddb.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
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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
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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
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// 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
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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
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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
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// 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
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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
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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。
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// 开始关联模式var user Userdb.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() |
以上就是golang gorm的关系关联实现示例的详细内容，更多关于golang gorm的关系关联的资料请关注服务器之家其它相关文章！
原文链接：https://www.cnblogs.com/guyouyin123/p/14115312.html
