gormExample/association.go

package gormExample

import (
	"fmt"
	"gorm.io/gorm/clause"
	"log"
)

func StdAssocModel() {
	// 利用migrate创建表
	// 以及多对多的关联表
	// 以及外键约束
	if err := DB.AutoMigrate(&Author{}, &Essay{}, &Tag{}, &EssayMate{}); err != nil {
		log.Fatalln(err)
	}
	// CREATE TABLE `msb_author` (
	//  `id` bigint unsigned NOT NULL AUTO_INCREMENT,
	//  `created_at` datetime(3) DEFAULT NULL,
	//  `updated_at` datetime(3) DEFAULT NULL,
	//  `deleted_at` datetime(3) DEFAULT NULL,
	//  `status` bigint DEFAULT NULL,
	//  `name` longtext,
	//  `email` longtext,
	//  PRIMARY KEY (`id`),
	//  KEY `idx_msb_author_deleted_at` (`deleted_at`)
	//) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

	// CREATE TABLE `msb_essay` (
	//  `id` bigint unsigned NOT NULL AUTO_INCREMENT,
	//  `created_at` datetime(3) DEFAULT NULL,
	//  `updated_at` datetime(3) DEFAULT NULL,
	//  `deleted_at` datetime(3) DEFAULT NULL,
	//  `subject` longtext,
	//  `content` longtext,
	//  `author_id` bigint unsigned DEFAULT NULL,
	//  PRIMARY KEY (`id`),
	//  KEY `idx_msb_essay_deleted_at` (`deleted_at`),
	//  KEY `fk_msb_author_essays` (`author_id`),
	//  CONSTRAINT `fk_msb_author_essays` FOREIGN KEY (`author_id`) REFERENCES `msb_author` (`id`)
	//) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

	// CREATE TABLE `msb_essay_mate` (
	//  `id` bigint unsigned NOT NULL AUTO_INCREMENT,
	//  `created_at` datetime(3) DEFAULT NULL,
	//  `updated_at` datetime(3) DEFAULT NULL,
	//  `deleted_at` datetime(3) DEFAULT NULL,
	//  `keyword` longtext,
	//  `description` longtext,
	//  `essay_id` bigint unsigned DEFAULT NULL,
	//  PRIMARY KEY (`id`),
	//  KEY `idx_msb_essay_mate_deleted_at` (`deleted_at`),
	//  KEY `fk_msb_essay_essay_mate` (`essay_id`),
	//  CONSTRAINT `fk_msb_essay_essay_mate` FOREIGN KEY (`essay_id`) REFERENCES `msb_essay` (`id`)
	//) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

	// CREATE TABLE `msb_tag` (
	//  `id` bigint unsigned NOT NULL AUTO_INCREMENT,
	//  `created_at` datetime(3) DEFAULT NULL,
	//  `updated_at` datetime(3) DEFAULT NULL,
	//  `deleted_at` datetime(3) DEFAULT NULL,
	//  `title` longtext,
	//  PRIMARY KEY (`id`),
	//  KEY `idx_msb_tag_deleted_at` (`deleted_at`)
	//) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci

	// CREATE TABLE `msb_essay_tag` (
	//  `tag_id` bigint unsigned NOT NULL,
	//  `essay_id` bigint unsigned NOT NULL,
	//  PRIMARY KEY (`tag_id`,`essay_id`),
	//  KEY `fk_msb_essay_tag_essay` (`essay_id`),
	//  CONSTRAINT `fk_msb_essay_tag_essay` FOREIGN KEY (`essay_id`) REFERENCES `msb_essay` (`id`),
	//  CONSTRAINT `fk_msb_essay_tag_tag` FOREIGN KEY (`tag_id`) REFERENCES `msb_tag` (`id`)
	//) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
	log.Println("migrate successful")
}

// 添加关联
func AssocAppend() {
	// A：一对多的关系, Author 1:n Essay
	// 创建测试数据
	var a Author
	a.Name = "一位作者"
	if err := DB.Create(&a).Error; err != nil {
		log.Println(err)
	}
	log.Println("a:", a.ID)
	var e1, e2 Essay
	e1.Subject = "一篇内容"
	//e1.AuthorID = a.ID
	e2.Subject = "另一篇内容"
	if err := DB.Create([]*Essay{&e1, &e2}).Error; err != nil {
		log.Println(err)
	}
	log.Println("e1, e2: ", e1.ID, e2.ID)

	// 添加关联
	if err := DB.Model(&a).Association("Essays").Append([]Essay{e1}); err != nil {
		log.Println(err)
	}
	fmt.Println(len(a.Essays))
	// 基于当前的基础上，添加关联
	if err := DB.Model(&a).Association("Essays").Append([]Essay{e2}); err != nil {
		log.Println(err)
	}
	fmt.Println(len(a.Essays))
	// 添加后，a模型对象的Essays字段，自动包含了关联的Essay模型
	//fmt.Println(a.Essays)

	// B: Essay M:N TAg
	var t1, t2, t3 Tag
	t1.Title = "Go"
	t2.Title = "GORM"
	t3.Title = "Ma"
	if err := DB.Create([]*Tag{&t1, &t2, &t3}).Error; err != nil {
		log.Println(err)
	}
	log.Println("t1, t2, t3: ", t1.ID, t2.ID, t3.ID)

	// e1 t1, t3
	// e2 t1, t2, t3
	if err := DB.Model(&e1).Association("Tags").Append([]Tag{t1, t3}); err != nil {
		log.Println(err)
	}

	if err := DB.Model(&e2).Association("Tags").Append([]Tag{t1, t2, t3}); err != nil {
		log.Println(err)
	}

	// 关联表查看
	// mysql> select * from msb_essay_tag;
	//+--------+----------+
	//| tag_id | essay_id |
	//+--------+----------+
	//|      1 |       12 |
	//|      3 |       12 |
	//|      1 |       13 |
	//|      2 |       13 |
	//|      3 |       13 |
	//+--------+----------+

	// C, Belongs To. Essay N:1 Author
	var e3 Essay
	e3.Subject = "第三篇内容"
	if err := DB.Create([]*Essay{&e3}).Error; err != nil {
		log.Println(err)
	}
	log.Println("e3: ", e3.ID)

	log.Println(e3.Author)
	// 关联
	if err := DB.Model(&e3).Association("Author").Append(&a); err != nil {
		log.Println(err)
	}
	log.Println(e3.Author.ID)

	// 对一的关联，会导致关联被更新
	var a2 Author
	a2.Name = "另一位作者"
	if err := DB.Create(&a2).Error; err != nil {
		log.Println(err)
	}
	log.Println("a2:", a2.ID)
	if err := DB.Model(&e3).Association("Author").Append(&a2); err != nil {
		log.Println(err)
	}
	log.Println(e3.Author.ID)

}

func AssocReplace() {
	// A. 替换
	// 创建测试数据
	var a Author
	a.Name = "一位作者"
	if err := DB.Create(&a).Error; err != nil {
		log.Println(err)
	}
	log.Println("a:", a.ID)

	var e1, e2, e3 Essay
	e1.Subject = "一篇内容"
	e2.Subject = "另一篇内容"
	e3.Subject = "第三篇内容"
	if err := DB.Create([]*Essay{&e1, &e2, &e3}).Error; err != nil {
		log.Println(err)
	}
	log.Println("e1, e2, e3: ", e1.ID, e2.ID, e3.ID)

	// 添加关联
	if err := DB.Model(&a).Association("Essays").Replace([]Essay{e1, e3}); err != nil {
		log.Println(err)
	}
	fmt.Println(len(a.Essays))
	// 基于当前的基础上，添加关联
	if err := DB.Model(&a).Association("Essays").Replace([]Essay{e2, e3}); err != nil {
		log.Println(err)
	}
	fmt.Println(len(a.Essays))

}

func AssocDelete() {
	// B. 删除，外键的
	// 创建测试数据
	var a Author
	a.Name = "一位作者"
	if err := DB.Create(&a).Error; err != nil {
		log.Println(err)
	}
	log.Println("a:", a.ID)

	var e1, e2, e3 Essay
	e1.Subject = "一篇内容"
	e2.Subject = "另一篇内容"
	e3.Subject = "第三篇内容"
	if err := DB.Create([]*Essay{&e1, &e2, &e3}).Error; err != nil {
		log.Println(err)
	}
	log.Println("e1, e2, e3: ", e1.ID, e2.ID, e3.ID)

	// 添加关联
	if err := DB.Model(&a).Association("Essays").Replace([]Essay{e1, e2, e3}); err != nil {
		log.Println(err)
	}
	fmt.Println(len(a.Essays))

	if err := DB.Model(&a).Association("Essays").Delete([]Essay{e1, e3}); err != nil {
		log.Println(err)
	}
	fmt.Println(len(a.Essays))
	fmt.Println("------------------------")

	// B. 删除，多对多，关联表
	var t1, t2, t3 Tag
	t1.Title = "Go"
	t2.Title = "GORM"
	t3.Title = "Ma"
	if err := DB.Create([]*Tag{&t1, &t2, &t3}).Error; err != nil {
		log.Println(err)
	}
	log.Println("t1, t2, t3: ", t1.ID, t2.ID, t3.ID)
	// e1 t1, t3
	// e2 t1, t2, t3
	if err := DB.Model(&e1).Association("Tags").Append([]Tag{t1, t2, t3}); err != nil {
		log.Println(err)
	}
	fmt.Println(len(e1.Tags))

	if err := DB.Model(&e1).Association("Tags").Delete([]Tag{t1, t3}); err != nil {
		log.Println(err)
	}
	fmt.Println(len(e1.Tags))

	// C. 清空关联
	if err := DB.Model(&e1).Association("Tags").Clear(); err != nil {
		log.Println(err)
	}
	fmt.Println(len(e1.Tags))
}

func AssocFind() {
	//
	e := Essay{}
	DB.First(&e, 18)

	// 查询关联的tags
	//var ts []Tag
	if err := DB.Model(&e).Association("Tags").Find(&e.Tags); err != nil {
		log.Println(err)
	}
	log.Println(e.Tags)

	// 子句，要写在Association()方法前面
	if err := DB.Model(&e).
		Where("tag_id > ?", 7).
		Order("tag_id DESC").
		Association("Tags").Find(&e.Tags); err != nil {
		log.Println(err)
	}
	log.Println(e.Tags)

	// 查询关联的模型的数量
	count := DB.Model(&e).Association("Tags").Count()
	log.Println("count:", count)

}

func AssocSave() {
	var t1 Tag
	DB.First(&t1, 10)

	e := Essay{
		Subject: "一个组合的Save",
		Author:  Author{Name: "马士兵"},
		Tags: []Tag{
			t1,
			{Title: "Ma"},
			{Title: "GORM"},
		},
	}

	if err := DB.Save(&e).Error; err != nil {
		log.Println(err)
	}

	log.Printf("%+v\n", e)

}

// Preload
func AssocPreload() {
	// A.直接一步查询Author对应的Essays
	a := Author{}
	if err := DB.
		Preload("Essays").
		First(&a, 1).Error; err != nil {
		log.Fatalln(err)
	}
	// [3.840ms] [rows:2] SELECT * FROM `msb_essay` WHERE `msb_essay`.`author_id` = 1 AND `msb_essay`.`deleted_at` IS NULL
	// [13.014ms] [rows:1] SELECT * FROM `msb_author` WHERE `msb_author`.`id` = 1 AND `msb_author`.`deleted_at` IS NULL ORDER BY `msb_author`.`id` LIMIT 1
	log.Println(a.Essays)
	log.Println("--------------------")

	// B.支持条件过滤
	if err := DB.
		Preload("Essays", "id IN ?", []uint{2, 3, 4}).
		First(&a, 1).Error; err != nil {
		log.Fatalln(err)
	}
	// [3.217ms] [rows:1] SELECT * FROM `msb_essay` WHERE `msb_essay`.`author_id` = 1 AND id IN (2,3,4) AND `msb_essay`.`deleted_at` IS NULL
	log.Println(a.Essays)
	log.Println("-----------------------")

	// C. 支持多次链式调用，同时预加载多个关联
	e := Essay{}
	if err := DB.
		//Preload("Author").
		//Preload("EssayMate").
		//Preload("Tags").
		Preload(clause.Associations).
		First(&e, 1).Error; err != nil {
		log.Fatalln(err)
	}
	log.Println(e)
	// [2.776ms] [rows:1] SELECT * FROM `msb_author` WHERE `msb_author`.`id` = 1 AND `msb_author`.`deleted_at` IS NULL
	// [10.398ms] [rows:0] SELECT * FROM `msb_essay_mate` WHERE `msb_essay_mate`.`essay_id` = 1 AND `msb_essay_mate`.`deleted_at` IS NULL
	// [3.260ms] [rows:2] SELECT * FROM `msb_essay_tag` WHERE `msb_essay_tag`.`essay_id` = 1
	// [3.264ms] [rows:2] SELECT * FROM `msb_tag` WHERE `msb_tag`.`id` IN (1,3) AND `msb_tag`.`deleted_at` IS NULL
	// [28.067ms] [rows:1] SELECT * FROM `msb_essay` WHERE `msb_essay`.`id` = 1 AND `msb_essay`.`deleted_at` IS NULL ORDER BY `msb_essay`.`id` LIMIT 1
}

// 多级
func AssocLevelPreload() {
	a := Author{}
	if err := DB.
		//Preload("Essays").
		// 多级关联
		Preload("Essays.Tags").
		First(&a, 1).Error; err != nil {
		log.Fatalln(err)
	}
	// [3.843ms] [rows:5] SELECT * FROM `msb_essay_tag` WHERE `msb_essay_tag`.`essay_id` IN (1,2)
	// [3.284ms] [rows:3] SELECT * FROM `msb_tag` WHERE `msb_tag`.`id` IN (1,3,2) AND `msb_tag`.`deleted_at` IS NULL
	// [10.396ms] [rows:2] SELECT * FROM `msb_essay` WHERE `msb_essay`.`author_id` = 1 AND `msb_essay`.`deleted_at` IS NULL
	// [17.609ms] [rows:1] SELECT * FROM `msb_author` WHERE `msb_author`.`id` = 1 AND `msb_author`.`deleted_at` IS NULL ORDER BY `msb_author`.`id` LIMIT 1

	log.Println(a.Essays[0].Tags)
	log.Println(a.Essays[1].Tags)
}

func AssocOperate() {
	// 创建测试数据
	var a Author
	a.Name = "一位作者"
	if err := DB.Create(&a).Error; err != nil {
		log.Println(err)
	}
	log.Println("a:", a.ID)
	var e1, e2 Essay
	e1.Subject = "一篇内容"
	//e1.AuthorID = a.ID
	e2.Subject = "另一篇内容"
	if err := DB.Create([]*Essay{&e1, &e2}).Error; err != nil {
		log.Println(err)
	}
	log.Println("e1, e2: ", e1.ID, e2.ID)
	// 基于当前的基础上，添加关联
	if err := DB.Model(&a).Association("Essays").Append([]Essay{e1, e2}); err != nil {
		log.Println(err)
	}
	fmt.Println(len(a.Essays))

	// 删除a,注意essays的处理
	if err := DB.Unscoped().Delete(&a).Error; err != nil {
		log.Fatalln(err)
	}
}