Defining foreign key relationships in Go using GORM [duplicate] - sql

Question

I have those two models:
User model:
type User struct {
DBBase
Email string `gorm:"column:email" json:"email"`
Password string `gorm:"column:password" json:"-"`
}
func (User) TableName() string {
return "t_user"
}
User info model:
type UserInfo struct {
User User `gorm:"foreignkey:u_id;association_foreignkey:id"`
UID uint `gorm:"column:u_id" json:"-"`
FirstName string `gorm:"column:first_name" json:"first_name"`
LastName string `gorm:"column:last_name" json:"last_name"`
Phone string `gorm:"column:phone" json:"phone"`
Address string `gorm:"column:address" json:"address"`
}
func (UserInfo) TableName() string {
return "t_user_info"
}
and I want to make UID related to the id of the user table.
this is the function that creates the user:
func (dao *AuthDAO) Register(rs app.RequestScope, user *models.User, userInfo *models.UserInfo) (userErr error, userInfoErr error) {
createUser := rs.Db().Create(&user)
userInfo.UID = user.ID
createUserInfo := rs.Db().Create(&userInfo)
return createUser.Error, createUserInfo.Error
}
I did try what gorm wrote on the documentation, but without success:
http://doc.gorm.io/associations.html

Answer 1

Note!
from gorm 2.0 this is no longer necessary, read more here:
gorm.io/docs/belongs_to.html#FOREIGN-KEY-Constraints
The solution is to add this line when migrating the database:
db.Model(&models.UserInfo{}).AddForeignKey("u_id", "t_user(id)", "RESTRICT", "RESTRICT")
migration (gorm documentation)

Answer 2

I found the following code correctly created the foreign key without having to do any custom migration code; just the usual AutoMigrate.
type Account struct {
ID uint `gorm:"primary_key"`
}
type Transaction struct {
ID uint `gorm:"primary_key"`
AccountID uint
Account Account `gorm:"constraint:OnUpdate:CASCADE,OnDelete:CASCADE;"`
}
I am using "Gorm 2.0" which is a dependency of gorm.io/gorm v1.23.3.

Answer 3

Read about the belongs to relationship in https://gorm.io/docs/belongs_to.html
Also, there's a good example here: https://medium.com/#the.hasham.ali/how-to-use-uuid-key-type-with-gorm-cc00d4ec7100
// User is the model for the user table.
type User struct {
Base
SomeFlag bool `gorm:"column:some_flag;not null;default:true"`
Profile Profile
}// Profile is the model for the profile table.
type Profile struct {
Base
Name string `gorm:"column:name;size:128;not null;"`
UserID uuid.UUID `gorm:"type:uuid;column:user_foreign_key;not null;"`
}

Answer 4

We can add foreign key constraints in the latest version using CreateConstraint.
Example:
Suppose we have two entity
type User struct {
gorm.Model
CreditCards []CreditCard
}
type CreditCard struct {
gorm.Model
Number string
UserID uint
}
Now create database foreign key for user & credit_cards
db.Migrator().CreateConstraint(&User{}, "CreditCards")
db.Migrator().CreateConstraint(&User{}, "fk_users_credit_cards")
which translates to the following SQL code for Postgres:
ALTER TABLE `credit_cards` ADD CONSTRAINT `fk_users_credit_cards` FOREIGN KEY (`user_id`) REFERENCES `users`(`id`)
Referrence:
Gorm official doc for Constraint Creation
Changes in the latest version

Answer 5

For recent release of Gorm i.e. 1.21.xIf you have a one to one mapping of fields and not have parent to child mapping, here is what you will do
type BaseConfig struct {
ID uuid.UUID `gorm:"primary_key" json:"id"`
}
type Ledger struct {
BaseConfigId uuid.UUID `json:"base_config_id"`
BaseConfig BaseConfig `gorm:"column:base_config_id;constraint:OnUpdate:CASCADE,OnDelete:SET NULL;"`
}
In Migration script you will need to follow as per docs
WriteClient.Migrator().CreateConstraint(&models.BaseConfig{}, "Ledgers")
WriteClient.Migrator().CreateConstraint(&models.BaseConfig{}, "fk_base_configs_id")
I feel the tripping point is the missing documentation for how to associate. Some juggling around could be there to figure it out, so hope my answer saves some time.