gorm 使用介绍

本文介绍go中grom的使用。ORM(Object Relation Mapping, 关系对象映射)可以把Golang Struct模型对象映射到关系型数据库结构中。

介绍

gorm 是使用 golang 语言开发的 ORM 库，源码地址：https://github.com/go-gorm/gorm

关系型数据库与Golang对象的对应关系如下：

gorm 的部分特性：

• 添加struct属性，支持自动 migrate 变化到数据库

• 删除struct属性，不会删除数据库的列

• db migrate 详细参考

• Declaring Models

type Abc struct {
  ID        uint           `gorm:"primaryKey;auto_increment"`
  Name      string         `gorm:"type:varchar(32); size:32; not null; unique; default:''"`
  CreatedAt time.Time      `gorm:"type:date"`
  UpdatedAt time.Time
  DeletedAt gorm.DeletedAt `gorm:"index"`
}

• 调整表名
• Many to Many

示例

package main

import (
	"fmt"
	"log"
	"os"
	"time"

	"gorm.io/driver/sqlite"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
)

type Product struct {
	gorm.Model
	Code  string
	Price uint
}

func main() {
	newLogger := logger.New(
		log.New(os.Stdout, "\r\n", log.LstdFlags), // io writer
		logger.Config{
			SlowThreshold:             time.Second, // Slow SQL threshold
			LogLevel:                  logger.Info, // Log level
			IgnoreRecordNotFoundError: true,        // Ignore ErrRecordNotFound error for logger
			Colorful:                  false,       // Disable color
		},
	)

	db, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{Logger: newLogger})
	if err != nil {
		panic("failed to connect database")
	}

	// Migrate the schema
	db.AutoMigrate(&Product{})

	// Create
	db.Create(&Product{Code: "D42", Price: 100})

	// Read
	var product Product
	db.First(&product, 1)                 // find product with integer primary key
	db.First(&product, "code = ?", "D42") // find product with code D42

	fmt.Println(product)

	var p1 Product
	db.Last(&p1)
	fmt.Println(p1)
	var ps []Product
	db.Find(&ps, "code like ?", "D%")
	fmt.Println(ps)

	// Update - update product's price to 200
	db.Model(&product).Update("Price", 200)
	// Update - update multiple fields
	db.Model(&product).Updates(Product{Price: 200, Code: "F42"}) // non-zero fields
	db.Model(&product).Updates(map[string]interface{}{"Price": 200, "Code": "F42"})

	// Delete - delete product
	db.Delete(&product, 1)
}
view raw /golang/gorm/gormdemo.go