t.Fatalf("errors happened when create: %v", err)
	}

	user.Pets = []*Pet{{Name: "pet1"}, {Name: "pet2"}}
	if err := DB.Save(&user).Error; err != nil {
		t.Fatalf("errors happened when update: %v", err)
	}

	var user2 User
	DB.Preload("Pets").Find(&user2, "id = ?", user.ID)
	CheckUser(t, user2, user)

	for _, pet := range user.Pets {
		pet.Name += "new"
	}

	if err := DB.Save(&user).Error; err != nil {

// He speaks many languages (many to many) and has many friends (many to many - single-table)
// His pet also has one Toy (has one - polymorphic)
// NamedPet is a reference to a named `Pet` (has one)
type User struct {
	gorm.Model
	Name      string
	Age       uint
	Birthday  *time.Time
	Account   Account
	Pets      []*Pet
	NamedPet  *Pet
	Toys      []Toy   `gorm:"polymorphic:Owner"`

		t.Errorf("Table with escape character, got %v", r.Statement.SQL.String())
	}

	r = dryDB.Table("(?) as u, (?) as p", DB.Model(&User{}).Select("name"), DB.Model(&Pet{}).Select("name")).Find(&User{}).Statement

	"time"

	"gorm.io/gorm"
	"gorm.io/gorm/utils/tests"
)

type User struct {
	*gorm.Model
	Name      *string
	Age       *uint
	Birthday  *time.Time
	Account   *tests.Account
	Pets      []*tests.Pet
	Toys      []*tests.Toy `gorm:"polymorphic:Owner"`
	CompanyID *int
	Company   *tests.Company
	ManagerID *uint
	Manager   *User
	Team      []*User           `gorm:"foreignkey:ManagerID"`

	} else if debug == "false" {
		db.Logger = db.Logger.LogMode(logger.Silent)
	}

	return
}

func RunMigrations() {
	var err error
	allModels := []interface{}{&User{}, &Account{}, &Pet{}, &Company{}, &Toy{}, &Language{}, &Coupon{}, &CouponProduct{}, &Order{}, &Parent{}, &Child{}, &Tools{}}
	rand.Seed(time.Now().UnixNano())

			}
			relationships.Relations[relation.Name] = relation
		}
	}
}

// User has many Toys, its `Polymorphic` is `Owner`, Pet has one Toy, its `Polymorphic` is `Owner`
//
//	type User struct {
//	  Toys []Toy `gorm:"polymorphic:Owner;"`
//	}
//	type Pet struct {
//	  Toy Toy `gorm:"polymorphic:Owner;"`
//	}
//	type Toy struct {
//	  OwnerID   int
//	  OwnerType string
//	}

			References: []Reference{{"ID", "User", "UserID", "Account", "", true}},
		},
		{
			Name: "Pets", Type: schema.HasMany, Schema: "User", FieldSchema: "Pet",
			References: []Reference{{"ID", "User", "UserID", "Pet", "", true}},
		},
		{
			Name: "Toys", Type: schema.HasMany, Schema: "User", FieldSchema: "Toy",
			Polymorphic: Polymorphic{ID: "OwnerID", Type: "OwnerType", Value: "users"},

	}

	DB.Where(&User{Name: "find or create embedded struct"}).Assign(User{Age: 44, Account: Account{Number: "1231231231"}, Pets: []*Pet{{Name: "first_or_create_pet1"}, {Name: "first_or_create_pet2"}}}).FirstOrCreate(&user8)
	if err := DB.Where("name = ?", "first_or_create_pet1").First(&Pet{}).Error; err != nil {
		t.Errorf("has many association should be saved")
	}

So, `orion_cat.owner.name` could be the name (from the `name` column in the `owners` table) of this pet's owner.

It could have a value like `"Arquilian"`.

And the ORM will do all the work to get the information from the corresponding table *owners* when you try to access it from your pet object.

**FastAPI**可与任何数据库在任何样式的库中一起与 数据库进行通信。

一种常见的模式是使用“ORM”：对象关系映射。

ORM 具有在代码和数据库表（“*关系型”）中的**对象**之间转换（“*映射*”）的工具。

使用 ORM，您通常会在 SQL 数据库中创建一个代表映射的类，该类的每个属性代表一个列，具有名称和类型。

例如，一个类`Pet`可以表示一个 SQL 表`pets`。

该类的每个*实例对象都代表数据库中的一行数据。*

又例如，一个对象`orion_cat`（`Pet`的一个实例）可以有一个属性`orion_cat.type`, 对标数据库中的`type`列。并且该属性的值可以是其它，例如`"cat"`。

这些 ORM 还具有在表或实体之间建立关系的工具（比如创建多表关系）。

这样，您还可以拥有一个属性`orion_cat.owner`，它包含该宠物所有者的数据，这些数据取自另外一个表。