[golang gin框架] 7.Gin GORM增删改查以及查询语句详解
1.GORM CURD
找到要操作数据库表的控制器，然后引入 models 模块
models/user.go
package models
type User struct { // 结构体首字母大写, 和数据库表名对应, 默认访问数据表users, 可以设置访问数据表的方法
Id int
Username string
Age int
Email string
AddTime int // 大驼峰命名
}
//配置数据库操作的表名称
func (User) TableName() string {
return "user"
}(1).添加数据
增加成功后会返回刚才增加的记录
//添加数据
func (con UserController) Add(c *gin.Context) {
user := &models.User{
Username: "张三",
Age: 12,
Email: "[email protected]",
AddTime: int(models.GetUnix()),
}
err := models.DB.Create(user).Error // 通过数据的指针来创建
if err != nil {
fmt.Println(err)
return
}
fmt.Println(user)
c.String(200, "增加数据成功")
}更多添加语句见文档:https://gorm.io/zh_CN/docs/create.html
(2).查找
func (con UserController) Index(c *gin.Context) {
//查找全部
userList := []models.User{}
//查询所有用户,把结果保存到userList切片中
models.DB.Find(&userList)
c.JSON(http.StatusOK, gin.H{
"result": userList,
})
//条件查询
//查询age大于30的用户
//查询数据库
userList := []models.User{}
models.DB.Where("age > ?", 30).Find(&userList)
c.JSON(http.StatusOK, gin.H{
"result": userList,
})
}更多查询语句：https://gorm.io/zh_CN/docs/query.html
(3).修改
func (con UserController) Edit(c *gin.Context) {
//查询id等于5的字段
user := models.User{Id: 5}
models.DB.Find(&user)
c.JSON(200, gin.H{
"user": user,
})
//更新所有数据
user.Username = "你好"
user.Age = 111
models.DB.Save(&user)
//更新单个列
user1 := models.User{}
models.DB.Model(&user1).Where("id = ?", 9).Update("username", "大")
//一般情况的更新
user2 := models.User{}
models.DB.Where("id = ?", 1).Find(&user2)
user2.Username = "好"
user2.Age = 31
models.DB.Save(&user2)
}更多修改的方法参考：https://gorm.io/zh_CN/docs/update.html
(4).删除
//删除数据
func (conn UserController) Delete(c *gin.Context) {
user := models.User{Id: 1}
models.DB.Delete(&user)
//删除数据
user1 := models.User{}
models.DB.Where("Age = ?", 31).Delete(&user1)
}更多删除的方法参考:https://gorm.io/zh_CN/docs/delete.html
2.GORM 查询语句详解
(1).查询全部数据
//查询全部数据
list := []models.Nav{}
//把结果保存到list切片中
models.DB.Find(&list)
c.JSON(http.StatusOK, gin.H{
"result": list,
})(2).查询一条数据
//查询一条数据
nav := models.Nav{Id: 21}
models.DB.Find(&nav)
c.JSON(http.StatusOK, gin.H{
"result": nav,
})
nav1 := models.Nav{}
models.DB.First(&nav1, "21")
c.JSON(http.StatusOK, gin.H{
"result": nav1,
})
nav2 := models.Nav{}
models.DB.Model(models.Nav{Id: 21}).First(&nav2)
c.JSON(http.StatusOK, gin.H{
"result": nav2,
})(3).Where
=,<,>,<=,>=,!=,IS NOT NULL,IS NULL,BETWEEN AND,NOT BETWEEN AND,IN,OR,AND,NOT,LIKE查询
查询id>3的数据
nav := []models.Nav{}
models.DB.Where("id > ?", 3).Find(&nav)
c.JSON(http.StatusOK, gin.H{
"result": nav,
})
//查询id>3 并且 id < 9 的数据
nav1 := []models.Nav{}
models.DB.Where("id > ? and id < ?", 3, 9).Find(&nav1)
c.JSON(http.StatusOK, gin.H{
"result": nav1,
})
//查询id=3,5,6的数据
nav2 := []models.Nav{}
models.DB.Where("id in ?", []int{3, 5, 6}).Find(&nav2)
c.JSON(http.StatusOK, gin.H{
"result": nav2,
})
//查询标题包含 '会'的内容
nav3 := []models.Nav{}
models.DB.Where("title like ?", "%会%").Find(&nav3)
c.JSON(http.StatusOK, gin.H{
"result": nav3,
})
//查询id>3 并且 id < 9 的数据,使用between and
nav4 := []models.Nav{}
models.DB.Where("id between ? and ?", 3, 9).Find(&nav4)
c.JSON(http.StatusOK, gin.H{
"result": nav4,
})
//查询id=2或者iD=3的数据
//方法一
nav5 := []models.Nav{}
models.DB.Where("id = ? or id = ?", 3, 9).Find(&nav5)
c.JSON(http.StatusOK, gin.H{
"result": nav5,
})
//方法二
nav6 := []models.Nav{}
models.DB.Where("id = ?", 2).Or("id = ?", 3).Find(&nav6)
c.JSON(http.StatusOK, gin.H{
"result": nav6,
})(4).选择字段查询
//使用select返回指定的字段, 使用结构体时,没有的数据会默认为0或""
nav7 := []models.Nav{}
models.DB.Select("title", "id").Where("id = ?", 2).Or("id = ?", 3).Find(&nav7)
c.JSON(http.StatusOK, gin.H{
"result": nav7,
})(5).排序 Limit 、Offset
//order排序, limit, Offset
nav8 := []models.Nav{}
models.DB.Order("id desc").Find(&nav8)
c.JSON(http.StatusOK, gin.H{
"result": nav8,
})
nav9 := []models.Nav{}
models.DB.Order("id desc").Limit(3).Find(&nav9)
c.JSON(http.StatusOK, gin.H{
"result": nav9,
})
//分页
nav10 := []models.Nav{}
models.DB.Order("id desc").Offset(2).Limit(3).Find(&nav10)
c.JSON(http.StatusOK, gin.H{
"result": nav10,
})(6).count计数
nav11 := []models.Nav{}
var num int64
models.DB.Where("id > ? and id < ?", 3, 9).Find(&nav11).Count(&num)
c.JSON(http.StatusOK, gin.H{
"result": num,
})(7).Distinct
从模型中选择不相同的值
nav := []models.Nav{}
models.DB.Distinct("title").Order("id desc").Find(&nav)
c.JSON(200, gin.H{
"nav": nav,
})
//SELECT DISTINCT `title` FROM `nav` ORDER BY id desc(8).Scan
将结果扫描到结构中的方法与我们使用find的方法类似
type Result struct {
Name string
Age int
}
var result Result
models.DB.Table("users").Select("name", "age").Where("name = ?", "Antonio").Scan(&result)
// 原生 SQL
models.DB.Raw("SELECT name, age FROM users WHERE name = ?", "Antonio").Scan(&result)
var result []models.User
models.DB.Raw("SELECT * FROM user").Scan(&result)
fmt.Println(result)(9).Joins
查询内联
type result struct {
Name string
Email string
}
db.Model(&User{}).Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Scan(&result{})
// SELECT users.name, emails.email FROM `users` left join emails on emails.user_id = users.id
rows, err := db.Table("users").Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Rows()
for rows.Next() {
...
}
db.Table("users").Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Scan(&results)
// multiple joins with parameter
db.Joins("JOIN emails ON emails.user_id = users.id AND emails.email = ?", "[email protected]").Joins("JOIN credit_cards ON credit_cards.user_id = users.id").Where("credit_cards.number = ?", "411111111111").Find(&user)//Joins 预加载
You can use Joins eager loading associations with a single SQL, for example:
db.Joins("Company").Find(&users)
// SELECT `users`.`id`,`users`.`name`,`users`.`age`,`Company`.`id` AS `Company__id`,`Company`.`name` AS `Company__name` FROM `users` LEFT JOIN `companies` AS `Company` ON `users`.`company_id` = `Company`.`id`;
// inner join
db.InnerJoins("Company").Find(&users)
// SELECT `users`.`id`,`users`.`name`,`users`.`age`,`Company`.`id` AS `Company__id`,`Company`.`name` AS `Company__name` FROM `users` INNER JOIN `companies` AS `Company` ON `users`.`company_id` = `Company`.`id`;
Join with conditions
db.Joins("Company", db.Where(&Company{Alive: true})).Find(&users)
// SELECT `users`.`id`,`users`.`name`,`users`.`age`,`Company`.`id` AS `Company__id`,`Company`.`name` AS `Company__name` FROM `users` LEFT JOIN `companies` AS `Company` ON `users`.`company_id` = `Company`.`id` AND `Company`.`alive` = true;
For more details, please refer to Preloading (Eager Loading).
Joins 一个衍生表
You can also use Joins to join a derived table.
type User struct {
Id int
Age int
}
type Order struct {
UserId int
FinishedAt *time.Time
}
query := db.Table("order").Select("MAX(order.finished_at) as latest").Joins("left join user user on order.user_id = user.id").Where("user.age > ?", 18).Group("order.user_id")
db.Model(&Order{}).Joins("join (?) q on order.finished_at = q.latest", query).Scan(&results)
// SELECT `order`.`user_id`,`order`.`finished_at` FROM `order` join (SELECT MAX(order.finished_at) as latest FROM `order` left join user user on order.user_id = user.id WHERE user.age > 18 GROUP BY `order`.`user_id`) q on order.finished_at = q.latest(10).查看执行的失去了
package models
//gorm文档: https://gorm.io/zh_CN/docs/index.html
//连接数据库核心代码
import (
"fmt"
"gorm.io/gorm"
"gorm.io/driver/mysql"
)
//全局使用DB,就需要把DB定义成公有的
var DB *gorm.DB
var err error
//自动初始化数据库
func init() {
// 参考 https://github.com/go-sql-driver/mysql#dsn-data-source-name 获取详情
dsn := "root:123456@tcp(127.0.0.1:3306)/gin?charset=utf8mb4&parseTime=True&loc=Local"
DB, err = gorm.Open(mysql.Open(dsn), &gorm.Config{})
//查看执行的sql
DB.Debug()
if err != nil {
fmt.Println(err)
}
}更多查询语句:https://gorm.io/zh_CN/docs/query.html
[上一节]6.Gin GORM简介以及安装