ORM框架Gorm-Has Many

定义用户结构体和地址结构体

type User struct {
	gorm.Model
	Name     string
	Age      int
	Active   bool
	Addresss []Address
}

type Address struct {
	gorm.Model
	Name   string
	Code   string
	UserID uint
}

初始化数据库

var db *gorm.DB

func init() {
	dsn := "root:root@tcp(127.0.0.1:3306)/go_orm?charset=utf8mb4&parseTime=True&loc=Local"
	d, err := gorm.Open(mysql.Open(dsn), &gorm.Config{Logger: logger.Default.LogMode(logger.Info)})
	if err != nil {
		log.Fatal(err)
	}
	db = d
	db.AutoMigrate(&User{}, &Address{})
}

创建模拟数据

// 批量插入用户数据
func insertManyUser() {
	var users = []User{
		{Name: "1", Age: 1}, {Name: "2", Age: 2},
		{Name: "3", Age: 3}, {Name: "4", Age: 4},
	}
	d := db.Select("Name", "Age").Create(&users)
	fmt.Printf("d.RowsAffected: %vn", d.RowsAffected)
}

// 批量插入用户地址数据
func insertManyAddress() {
	var addresss = []Address{
		{Name: "1-1", Code: "code1", UserID: 1},
		{Name: "1-2", Code: "code2", UserID: 1},
		{Name: "2-1", Code: "code1", UserID: 2},
		{Name: "2-2", Code: "code2", UserID: 2},
		{Name: "2-3", Code: "code3", UserID: 2},
		{Name: "3-2", Code: "code1", UserID: 3},
	}
	d := db.Create(&addresss)
	fmt.Printf("d.RowsAffected: %vn", d.RowsAffected)
}

初始化模拟数据运行结果

查询单个人信息以及单个人下面地址信息加条件

func test() {
	var user User
	db.Model(&User{}).Where("id", 2).Find(&user)
	var addresss []Address
	// `user` 是源模型，它的主键不能为空
	// 关系的字段名是 `Addresss`
	db.Model(&user).Where("code IN ?", []string{"code1", "code3"}).Association("Addresss").Find(&addresss)
	user.Addresss = addresss
	fmt.Printf("user: %+vn", user)
}

为单个人添加一个地址信息或添加多个信息

func test() {
	// 为用户1添加地址1-3 code3
	var user1 User
	db.Model(&User{}).Where("id", 1).Find(&user1)
	db.Model(&user1).Association("Addresss").Append(&Address{Name: "1-3", Code: "code3"})

	// 为用户3添加地址3-1 code1 3-3 code3
	var user3 User
	db.Model(&User{}).Where("id", 3).Find(&user3)
	address31 := Address{Name: "3-1", Code: "code1"}
	address33 := Address{Name: "3-3", Code: "code3"}
	db.Model(&user3).Association("Addresss").Append([]Address{address31, address33})
}

运行后数据库结果如下

用一个新的关联替换当前关联(原来所有的关联变为新的关联)

func test() {
	// 为用户3替换地址3-1 code1 3-2 code2
	var user3 User
	db.Model(&User{}).Where("id", 3).Find(&user3)
	address31 := Address{Name: "3-1", Code: "code1"}
	address32 := Address{Name: "3-2", Code: "code2"}
	db.Model(&user3).Association("Addresss").Replace([]Address{address31, address32})
}

运行后数据库结果如下

查询用户下地址数量并进行条件筛选

func test() {
	var user1 User
	db.Model(&User{}).Where("id", 1).Find(&user1)

	// 关联计数
	i := db.Model(&user1).Association("Addresss").Count()
	fmt.Printf("i: %vn", i)
	// 提交件计数
	i2 := db.Model(&user1).Where("code IN ?", []string{"code1", "code4"}).Association("Addresss").Count()
	fmt.Printf("i2: %vn", i2)
}

运行结果

如果存在，则删除源模型与参数之间的关系，只会删除引用，不会从数据库中删除这些对象。

func test() {
	var user1 User
	db.Model(&User{}).Where("id", 1).Find(&user1)
	var user12, user13 Address
	db.Model(&Address{}).Where("id", 7).Find(&user13)
	// 注意这条不属于user1
	db.Model(&Address{}).Where("id", 10).Find(&user12)
	db.Model(&user1).Association("Addresss").Delete([]Address{user13, user12})
}

运行后数据库

删除源模型与关联之间的所有引用，但不会删除这些关联

func test() {
	var user3 User
	db.Model(&User{}).Where("id", 3).Find(&user3)
	db.Model(&user3).Association("Addresss").Clear()
}

运行后数据库结果如下

查询所有用户时候加载地址信息

func test() {
	var users []User
	db.Preload("Addresss").Find(&users)
	for _, user := range users {
		fmt.Printf("user.ID: %vn", user.ID)
		fmt.Printf("user.Name: %vn", user.Name)
		for _, address := range user.Addresss {
			fmt.Printf("address.ID: %vn", address.ID)
			fmt.Printf("address.Code: %vn", address.Code)
		}
	}
}

运行结果如下

查询用户表id在1，2中的用户并且预加载地址code在code1，code2的地址信息

func test() {
	var users []User
	db.Where("Id IN ?", []uint{1, 2}).Preload("Addresss", "code IN ?", []string{"code1", "code2"}).Find(&users)
	for _, user := range users {
		fmt.Printf("user: %v--%vn", user.ID, user.Name)
		for _, address := range user.Addresss {
			fmt.Printf("user: %v--%vn", address.ID, address.Code)
		}
	}
}

查询用户表id在1，2中的用户并且预加载地信息按照倒序排列

func test() {
	var users []User
	db.Where("Id IN ?", []uint{1, 2}).
		Preload("Addresss", func(db *gorm.DB) *gorm.DB {
			return db.Order("ID DESC")
		}).
		Find(&users)
	for _, user := range users {
		fmt.Printf("user: %v--%vn", user.ID, user.Name)
		for _, address := range user.Addresss {
			fmt.Printf("user: %v--%vn", address.ID, address.Code)
		}
	}
}