特殊说明：
gorm官方文档对foreign key 有这么一句话：To define a belongs to relationship, the foreign key must exists, default foreign key uses owner’s type name plus its primary key（要定义属于关系，外键必须存在，默认外键使用所有者的类型名及其主键）也就是说默认外键满足其所有者的类型名和主键
package main
import (
"fmt"
"github.com/jinzhu/gorm"
_ "github.com/jinzhu/gorm/dialects/postgres"
// 文章
type Topics struct {
Id int `gorm:"primary_key"`
Title string `gorm:"not null"`
UserId int `gorm:"not null"`
CategoryId int `gorm:"not null"`
Category Categories `gorm:"foreignkey:CategoryId"` //文章所属分类外键
User Users `gorm:"foreignkey:UserId"` //文章所属用户外键
// 用户
type Users struct {
Id int `gorm:"primary_key"`
Name string `gorm:"not null"`
// 分类
type Categories struct {
Id int `gorm:"primary_key"`
Name string `gorm:"not null"`
func GetDB() *gorm.DB {
db, err := gorm.Open("postgres", "postgres://postgres:root@localhost:5432/test?sslmode=disable")
if err != nil {
fmt.Println("db error:", err)
} else {
fmt.Println("database connection success")
//defer db.Close()
return db
func main() {
db := GetDB()
models := []interface{}{
&Topics{},
&Users{},
&Categories{},
//1.执行建表语句
err := db.Debug().AutoMigrate(models...).Error
if err != nil {
fmt.Println("db error:", err)
//2.执行sql
//INSERT INTO topics("id", "title", "user_id", "category_id") VALUES (1, '测试', 1, 1);
//INSERT INTO categories("id", "name") VALUES (1, '测试分类');
//INSERT INTO users("id", "name") VALUES (1, '测试用户');
//3.执行预加载
topics, err := GetTopicsById(db, 1)
if err != nil {
fmt.Println("get topics error:", err)
fmt.Println(topics)
func GetTopicsById(db *gorm.DB, id int) (*Topics, error) {
var topic Topics
//查询方法1
//err := db.Model(&topic).Where("id=?", id).First(&topic).
// Related(&topic.Category, "CategoryId").
// Related(&topic.User, "UserId").Error
//查询方法2
err := db.Where("id=?", id).
Preload("Category").
Preload("User").
First(&topic).Error
if err != nil {
return nil, err
return &topic, nil
参考文章：
