英文:
How to create one to one relationship and foreign key in gorm?
问题
Has One
, Has Many
, and Belongs To
are different types of relationships in database modeling, specifically in the context of object-relational mapping (ORM) frameworks like GORM.
-
Has One
: This relationship indicates that one model has a single associated model. In your example, theProfile
model has aHas One
relationship with theUser
model, meaning that eachProfile
instance is associated with one and only oneUser
instance. This relationship is typically represented by a foreign key in the associated model's table. -
Has Many
: This relationship indicates that one model has multiple associated models. In your example, there is no explicitHas Many
relationship defined, but it could be added if, for example, aUser
can have multipleProfile
instances. This relationship is typically represented by a foreign key in the associated model's table. -
Belongs To
: This relationship indicates that one model belongs to another model. In your example, theCategory
model has aBelongs To
relationship with theUser
model, meaning that eachCategory
instance is associated with one and only oneUser
instance. This relationship is typically represented by a foreign key in the model's table that belongs to another model.
To summarize, Has One
represents a one-to-one relationship, Has Many
represents a one-to-many relationship, and Belongs To
represents a many-to-one relationship.
英文:
What is the difference between Has One
, Has Many
and Belong To
I have 3 Models
User
Profile
Whereprofile
anduser
should haveone to one
relationshipCategory
Wherecategory
should beforeign key
touser
type User struct {
gorm.Model
Email *string
Name string
...
}
type Profile struct {
gorm.Model
Phone string
Address string
...
}
type Category struct {
gorm.Model
Name string
}
</details>
# 答案1
**得分**: 2
对于`User`拥有一个`Profile`的关系:
```go
type User struct {
gorm.Model
Email *string
Name string
Profile Profile // 这是关键的不同之处
}
type Profile struct {
gorm.Model
UserId int // 这是重要的
Phone string
Address string
}
对于Profile
属于一个User
的关系:
type User struct {
gorm.Model
Email *string
Name string
}
type Profile struct {
gorm.Model
UserId int // 这是重要的
User User // 这是关键的不同之处
Phone string
Address string
}
对于User
拥有多个Category
的关系:
type User struct {
gorm.Model
Email *string
Name string
CategoryList []Category
}
type Category struct {
gorm.Model
UserId int // 这是重要的
Name string
}
编辑:UserId
字段将成为你的外键。
如果你希望gorm自动为你创建表格,你可以在main.go中使用AutoMigrate
:
err := db.AutoMigrate(your_model_package.User{})
if err != nil {
return err
}
英文:
For User
Has One
Profile
type User struct {
gorm.Model
Email *string
Name string
Profile Profile //this is the key different
}
type Profile struct {
gorm.Model
UserId int //this is important
Phone string
Address string
}
For Profile
Belong To
User
type User struct {
gorm.Model
Email *string
Name string
}
type Profile struct {
gorm.Model
UserId int //this is important
User User //this is the key different
Phone string
Address string
}
For User
Has Many
Category
type User struct {
gorm.Model
Email *string
Name string
CategoryList []Category
}
type Category struct {
gorm.Model
UserId int //this is important
Name string
}
Edit: UserId field will become your foreign key.
If you want gorm to automatically create table for you, you can use AutoMigrate
in main.go
err := db.AutoMigrate(your_model_package.User{})
if err != nil {
return err
}
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