当前位置:网站首页>gorm 关联关系小结
gorm 关联关系小结
2022-07-07 21:53:00 【咳咳,您好请多指教!】
数据库设计
表1:
CREATE TABLE `blog_user` (
`id` int unsigned NOT NULL AUTO_INCREMENT,
`username` varchar(50) COLLATE utf8mb4_general_ci NOT NULL DEFAULT '',
`password` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL DEFAULT '',
`created_at` datetime(3) DEFAULT NULL,
`updated_at` datetime(3) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `idx_blog_user_created_at` (`created_at`),
KEY `idx_blog_user_updated_at` (`updated_at`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;
--------------------------------------------------------------------------------------------------------------------
表2:
CREATE TABLE `blog_article` (
`id` int unsigned NOT NULL AUTO_INCREMENT,
`title` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL DEFAULT '',
`user_id` bigint unsigned NOT NULL,
`is_hot` tinyint NOT NULL,
`created_at` datetime(3) DEFAULT NULL,
`updated_at` datetime(3) DEFAULT NULL,
`deleted_at` timestamp NULL DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=15 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;
1.Belongs To 属于
用户与文章的关系 文章表存在用户表的id 作为 外键 ,文章 属于 用户
1-1 User 的 Model 结构体
type User struct {
models.BaseModel
UserName string `gorm:"column:username;" json:"username"`
Password string `json:"-"`
models.CommonTimestampsField
}
1-2 Article 的 Model 结构体
type Article struct {
models.BaseModel
Title string `json:"title"`
IsHot int8 `json:"is_hot"`
UserId int64 `json:"user_id"` //外键
User users.User `json:"user" gorm:"ForeignKey:UserId"`//关联的对象
}
查询:
Joins 或 Preload 预加载
var results []Article
database.DB.Model(&Article{}).Joins("User").Find(&results).Error, results
2. hasOne 一对一
用户与文章的关系 文章表存在用户表的id 作为 外键 ,用户 与 文章 一对一 (假定 一个人只能有一片文章)
2-1 User 的 Model 结构体
type User struct {
models.BaseModel
UserName string `gorm:"column:username;" json:"username"`
Password string `json:"-"`
Article article.Article `gorm:"foreignKey:UserId"`//一对一关联
models.CommonTimestampsField
}
2-2 Article 的 Model 结构体
type Article struct {
models.BaseModel
Title string `json:"title"`
IsHot int8 `json:"is_hot"`
UserId int64 `json:"user_id"` //外键
}
查询:
Preload 预加载
var results []Article
database.DB.Model(&User{}).Preload("Article").Find(&results).Error, results
3.Has Many 一对多 用户与文章的关系 文章表存在用户表的id 作为 外键 ,用户 与 文章 一对多
3-1 User 的 Model 结构体
type User struct {
models.BaseModel
UserName string `gorm:"column:username;" json:"username"`
Password string `json:"-"`
Article []article.Article `gorm:"foreignKey:UserId"`
models.CommonTimestampsField
}
3-2 Article 的 Model 结构体
type Article struct {
models.BaseModel
Title string `json:"title"`
IsHot int8 `json:"is_hot"`
UserId int64 `json:"user_id"` //外键
}
查询:
Preload 预加载
var results []Article
database.DB.Model(&User{}).Preload("Article").Find(&results).Error, results
4.Many To Many
4-1.新增 是体表 language & blog_user_has_language
CREATE TABLE `blog_language` (
`id` int NOT NULL AUTO_INCREMENT,
`title` varchar(100) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL DEFAULT '',
`created_at` timestamp NULL DEFAULT NULL,
`updated_at` timestamp NULL DEFAULT NULL,
`deleted_at` timestamp NULL DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;
------------------------------------------------------------------------------------
CREATE TABLE `blog_user_has_language` (
`user_id` int NOT NULL DEFAULT '0',
`language_id` int NOT NULL DEFAULT '0'
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;
4-2.结构体
type User struct {
models.BaseModel
UserName string `gorm:"column:username;" json:"username"`
Password string `json:"-"`
Languages []language.Language `gorm:"many2many:user_has_language;"`
models.CommonTimestampsField
}
4-3.查询:
Preload 预加载
var results []Article
database.DB.Model(&User{}).Preload("Languages").Find(&results).Error, results
边栏推荐
- SAP HR social work experience 0023
- SAP HR奖罚信息导出
- postgres timestamp转人眼时间字符串或者毫秒值
- 【7.5】15. 三数之和
- B_QuRT_User_Guide(36)
- 产业共融新势能,城链科技数字峰会厦门站成功举办
- 数据分析系列 之3σ规则/依据拉依达准则来剔除异常值
- SAP HR 社会工作经历 0023
- [stm32+esp8266 connect Tencent cloud IOT development platform 2] stm32+esp8266-01s connect Tencent cloud
- 648. Word replacement
猜你喜欢
C inheritance and interface design polymorphism
Learn about scratch
Design and implementation of spark offline development framework
0-1 knapsack problem
SAP HR奖罚信息导出
New potential energy of industrial integration, Xiamen station of city chain technology digital summit successfully held
Home appliance industry channel business collaboration system solution: help home appliance enterprises quickly realize the Internet of channels
One week learning summary of STL Standard Template Library
Svn relocation
Anxinco EC series modules are connected to the multi protocol access products of onenet Internet of things open platform
随机推荐
Dataguard 主备清理归档设置
0-1 knapsack problem
S2b2b mall solution of intelligent supply chain in packaging industry: opening up a new ecosystem of e-commerce consumption
Balanced binary tree [AVL tree] - insert, delete
Possible SQL for Oracle table lookup information
The efficient s2b2c e-commerce system helps electronic material enterprises improve their adaptability in this way
C simple question one
First week of July
激光slam学习(2D/3D、偏实践)
ping报错:未知的名称或服务
KeePass realizes automatic input of web pages
SAP HR social work experience 0023
Sequence of entity layer, Dao layer, service layer and controller layer
Progress broadcast | all 29 shield machines of Guangzhou Metro Line 7 have been launched
JNI uses asan to check memory leaks
Get started with mongodb
PCB wiring rules of PCI Express interface
Anxin vb01 offline voice module access intelligent curtain guidance
Deep understanding of MySQL lock and transaction isolation level
Oracle string sorting