async def create_user(user: UserCreate):
    return user


@app.get("/pets/{pet_id}", response_model=PetOut)
async def read_pet(pet_id: int):
    user = UserDB(
        email="******@****.***",
        hashed_password="secrethashed",
    )
    pet = PetDB(name="Nibbler", owner=user)
    return pet


@app.get("/pets/", response_model=List[PetOut])
async def read_pets():
    user = UserDB(

			children, parent.Children)
	}
}

func TestAssociationError(t *testing.T) {
	user := *GetUser("TestAssociationError", Config{Pets: 2, Company: true, Account: true, Languages: 2})
	DB.Create(&user)

	var user1 User
	DB.Preload("Company").Preload("Pets").Preload("Account").Preload("Languages").First(&user1)

	var emptyUser User
	var err error
	// belongs to

	if !regexp.MustCompile("SELECT \\* FROM \\(SELECT .name. FROM .users. WHERE .users.\\..deleted_at. IS NULL\\) as u, \\(SELECT .name. FROM .pets. WHERE .pets.\\..deleted_at. IS NULL\\) as p WHERE .u.\\..deleted_at. IS NULL").MatchString(r.Statement.SQL.String()) {
		t.Errorf("Table with escape character, got %v", r.Statement.SQL.String())
	}

package tests

import (
	"database/sql"
	"time"

	"gorm.io/gorm"
)

// User has one `Account` (has one), many `Pets` (has many) and `Toys` (has many - polymorphic)
// He works in a Company (belongs to), he has a Manager (belongs to - single-table), and also managed a Team (has many - single-table)
// 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)

import (
	"database/sql"
	"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"`

	DB.Save(GetUser("joins-args-db", Config{Pets: 2}))

	if err := DB.Migrator().CreateView("invalid_users_pets",
		gorm.ViewOption{Query: nil}); err != gorm.ErrSubQueryRequired {
		t.Fatalf("no view should be created, got %v", err)
	}

	query := DB.Model(&User{}).
		Select("users.id as users_id, users.name as users_name, pets.id as pets_id, pets.name as pets_name").

	relations := []Relation{
		{
			Name: "Account", Type: schema.HasOne, Schema: "User", FieldSchema: "Account",
			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",

		t.Errorf("user should be found and updated with assigned attrs")
	}

	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")

**FastAPI** 👷 ⏮️ 🙆 💽 & 🙆 👗 🗃 💬 💽.

⚠ ⚓ ⚙️ "🐜": "🎚-🔗 🗺" 🗃.

🐜 ✔️ 🧰 🗜 ("*🗺*") 🖖 *🎚* 📟 & 💽 🏓 ("*🔗*").

⏮️ 🐜, 👆 🛎 ✍ 🎓 👈 🎨 🏓 🗄 💽, 🔠 🔢 🎓 🎨 🏓, ⏮️ 📛 & 🆎.

🖼 🎓 `Pet` 💪 🎨 🗄 🏓 `pets`.

& 🔠 *👐* 🎚 👈 🎓 🎨 ⏭ 💽.

🖼 🎚 `orion_cat` (👐 `Pet`) 💪 ✔️ 🔢 `orion_cat.type`, 🏓 `type`. & 💲 👈 🔢 💪, ✅ `"cat"`.

👫 🐜 ✔️ 🧰 ⚒ 🔗 ⚖️ 🔗 🖖 🏓 ⚖️ 👨‍💼.

## ORMs（对象关系映射）

**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）。