GO gin框架基础及gorm操作

Go gin 基础

package main

import (
   "fmt"
   "github.com/gin-gonic/gin"
   "html/template"
   "net/http"
)

type UserInfo struct {
   Username string `form:"username"`
   Password string `form:"password"`
}

func main() {
   r := gin.Default()
   // 加载静态文件
   r.Static("/xxx", "./static")
   r.SetFuncMap(template.FuncMap{ // 自定义过滤器
      "safe": func(str string) template.HTML {
         return template.HTML(str)
      },
   })
   r.LoadHTMLGlob("templates/*")

   // 模板渲染
   //r.GET("index", func(c *gin.Context) {
   // c.HTML(200, "index.html", gin.H{"title": "Hina"})
   //})

   // Get中query参数
   r.GET("web", func(c *gin.Context) {
      name := c.DefaultQuery("query", "Hina")
      c.JSON(200, gin.H{"name": name})
   })

   // POST中form参数
   r.GET("login", login)
   r.POST("login", login)

   // 获取请求的path(url)参数
   //r.GET("/:name/:age", func(c *gin.Context) {
   // name := c.Param("name")
   // age := c.Param("age")
   // fmt.Println(name, age)
   // c.JSON(200, gin.H{"name": name, "age": age})
   //})

   // 请求参数绑定结构体
   r.GET("user", user)
   r.POST("user", user)

   // 上传文件
   r.GET("file", func(c *gin.Context) {
      c.HTML(200, "index.html", gin.H{"title": "file"})
   })
   r.POST("upload", func(c *gin.Context) {
      fileobj, err := c.FormFile("f1")
      if err != nil {
         c.JSON(http.StatusBadGateway, gin.H{"error": err})
      } else {
         //filepath = fmt.Sprintf("./%s", fileobj.Filename)
         //filepath := path.Join("./", fileobj.Filename)
         c.SaveUploadedFile(fileobj, fileobj.Filename)
         c.JSON(200, gin.H{"s": "ok"})
      }
   })

   // 重定向
   r.GET("index", func(c *gin.Context) {
      //c.Redirect(301, "login")
      // 方法二
      c.Request.URL.Path="login"
      r.HandleContext(c)
   })

   // 路由与路由组
   


   r.Run(":8080")
}

func login(c *gin.Context) {
   if c.Request.Method == "GET" {
      c.HTML(200, "login.html", nil)
      return
   }
   username := c.PostForm("username")
   password := c.PostForm("password")
   c.JSON(200, gin.H{"username": username, "password": password})
   return
}

func user(c *gin.Context) {
   var u UserInfo // 声明一个UserInfo的结构体
   err := c.ShouldBind(&u)
   if err != nil {
      c.JSON(http.StatusBadRequest, gin.H{"error": err})
   } else {
      fmt.Printf("%#v\n", u)
      c.String(200, "OK")
   }
}

中间件

package main

import (
	"fmt"
	"github.com/gin-gonic/gin"
	"net/http"
	"time"
)

// 中间件

//定义一个中间件
func m1(c *gin.Context) {
	fmt.Println("m1 in....")
	//计时
	start := time.Now()

	//go func(c.Copy()) {}  // 使用goroutine时一定要用c的拷贝
	c.Next() //调用后续的处理函数
	//c.Abort() // 阻止调用后续的处理函数
	t2 := time.Since(start)
	fmt.Println(t2)
	fmt.Println("m1 out...")
}

func m2(c *gin.Context) {
	fmt.Println("m2 in....")
	if true {
		c.Set("name", "hina")
		c.Next()
	}
	//c.Next() //调用后续的处理函数
	//c.Abort() // 阻止调用后续的处理函数
	fmt.Println("m2 out...")
}

func AuthMiddleWare(args ...interface{}) gin.HandlerFunc {
	// 使用args参数去干别的事
	// 数据库查询
	// 条件判断
	return func(c *gin.Context) {
		// 处理业务逻辑
	}
}

func main() {
	r := gin.Default() // 默认使用Logger()和Recover中间件，不想使用可以 r:=gin.New()
	r.Use(m1, m2)      // 全局、路由组、单个视图函数
	r.GET("index", func(c *gin.Context) {
		fmt.Println("index...")
		name, _ := c.Get("name")
		c.JSON(http.StatusOK, gin.H{"isok": "ok", "name": name})
	})

	r.Run(":8080")
}

gorm基础

package main

import (
   "fmt"
   "github.com/jinzhu/gorm"
   _ "github.com/jinzhu/gorm/dialects/mysql"
)

// UserInfo --> 数据表
type UserInfo struct {
   ID     uint
   Name   string
   Gender string
   Hobby  string
}

func main() {
   //连接MySQL数据库
   db, err := gorm.Open("mysql", "root:123456@(localhost)/gorm?charset=utf8mb4&parseTime=true&loc=Local")
   if err != nil {
      panic(err)
   }
   defer db.Close()

   // 创建表、自动迁移(把结构体和数据表进行对应)
   db.AutoMigrate(&UserInfo{})

   // 创建数据行
   u1 := UserInfo{1, "Hina", "male", "read"}
   db.Create(&u1)

   // 查询
   var u UserInfo
   db.First(&u)  // 查询表中第一条数据保存到u中
   fmt.Println(u)

   // 更新
   db.Model(&u).Update("hobby", "write")

   db.Delete(&u)
}

grom表相关

package main

import (
   "database/sql"
   "github.com/jinzhu/gorm"
   _ "github.com/jinzhu/gorm/dialects/mysql"
   "time"
)

// 使用`AnimalID`作为主键
type Animal struct {
   AnimalID int64 `gorm:"primary_key"`
   Name     string
   Age      int64
}

// 唯一修改表名
func (Animal) TableName() string {
   return "Hina"
}

// 定义模型
type User struct {
   gorm.Model   // 内嵌
   Name         string
   Age          sql.NullInt64 // 零值类型
   Birthday     *time.Time
   Email        string  `gorm:"type:varchar(100);unique_index"`
   Role         string  `gorm:"size:255"`        // 设置字段大小为255
   MemberNumber *string `gorm:"unique;not null"` // 设置会员号（member number）唯一并且不为空
   Num          int     `gorm:"AUTO_INCREMENT"`  // 设置 num 为自增类型
   Address      string  `gorm:"index:addr"`      // 给address字段创建名为addr的索引
   IgnoreMe     int     `gorm:"-"`               // 忽略本字段
}

func main() {
   //连接MySQL数据库
   db, err := gorm.Open("mysql", "root:123456@(localhost)/gorm?charset=utf8mb4&parseTime=true&loc=Local")
   if err != nil {
      panic(err)
   }
   defer db.Close()

   // 修改默认表名规则
   gorm.DefaultTableNameHandler = func(db *gorm.DB, defaultTableName string) string {
      return "SMS_" + defaultTableName
   }

   db.SingularTable(true) // 禁用复数

   db.AutoMigrate(&User{})
   db.AutoMigrate(&Animal{})

   // 使用方法修改表名
   db.Table("biaoming").CreateTable(&User{})
}

type User struct {
	gorm.Model
	Name sql.NullString `gorm:"default:'rui'"`
	Age  int64
}

u := User{Name: sql.NullString{String: "",Valid: true}, Age: 18}
fmt.Println(db.NewRecord(&u)) // 判断主键是否为空 true
db.Debug().Create(&u)                 // 在数据库中创建了一条记录
fmt.Println(db.NewRecord(&u)) // 判断主键是否为空 false

CRUD

CRUD通常指数据库的增删改查操作，本文详细介绍了如何使用GORM实现创建、查询、更新和删除操作。

db*gorm.DB

import (
  "github.com/jinzhu/gorm"
  _ "github.com/jinzhu/gorm/dialects/mysql"
)

func main() {
  db, err := gorm.Open("mysql", "user:password@/dbname?charset=utf8&parseTime=True&loc=Local")
  defer db.Close()
  
  // db.Xx
}

创建

创建记录

首先定义模型：

type User struct {
	ID           int64
	Name         string
	Age          int64
}

NewRecord()Create()

user := User{Name: "q1mi", Age: 18}

db.NewRecord(user) // 主键为空返回`true`
db.Create(&user)   // 创建user
db.NewRecord(user) // 创建`user`后返回`false`

默认值

可以通过 tag 定义字段的默认值，比如：

type User struct {
  ID   int64
  Name string `gorm:"default:'小王子'"`
  Age  int64
}

注意：通过tag定义字段的默认值，在创建记录时候生成的 SQL 语句会排除没有值或值为 零值 的字段。 在将记录插入到数据库后，Gorm会从数据库加载那些字段的默认值。

举个例子：

var user = User{Name: "", Age: 99}
db.Create(&user)

INSERT INTO users("age") values('99');Name小王子

0""false零值Scanner/Valuer

使用指针方式实现零值存入数据库

// 使用指针
type User struct {
  ID   int64
  Name *string `gorm:"default:'小王子'"`
  Age  int64
}
user := User{Name: new(string), Age: 18))}
db.Create(&user)  // 此时数据库中该条记录name字段的值就是''

使用Scanner/Valuer接口方式实现零值存入数据库

// 使用 Scanner/Valuer
type User struct {
	ID int64
	Name sql.NullString `gorm:"default:'小王子'"` // sql.NullString 实现了Scanner/Valuer接口
	Age  int64
}
user := User{Name: sql.NullString{"", true}, Age:18}
db.Create(&user)  // 此时数据库中该条记录name字段的值就是''

扩展创建选项

PostgreSQL

// 为Instert语句添加扩展SQL选项
db.Set("gorm:insert_option", "ON CONFLICT").Create(&product)
// INSERT INTO products (name, code) VALUES ("name", "code") ON CONFLICT;

查询

一般查询

// 根据主键查询第一条记录
db.First(&user)
//// SELECT * FROM users ORDER BY id LIMIT 1;

// 随机获取一条记录
db.Take(&user)
//// SELECT * FROM users LIMIT 1;

// 根据主键查询最后一条记录
db.Last(&user)
//// SELECT * FROM users ORDER BY id DESC LIMIT 1;

// 查询所有的记录
db.Find(&users)
//// SELECT * FROM users;

// 查询指定的某条记录(仅当主键为整型时可用)
db.First(&user, 10)
//// SELECT * FROM users WHERE id = 10;

Where 条件

普通SQL查询

// Get first matched record
db.Where("name = ?", "jinzhu").First(&user)
//// SELECT * FROM users WHERE name = 'jinzhu' limit 1;

// Get all matched records
db.Where("name = ?", "jinzhu").Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu';

// <>
db.Where("name <> ?", "jinzhu").Find(&users)
//// SELECT * FROM users WHERE name <> 'jinzhu';

// IN
db.Where("name IN (?)", []string{"jinzhu", "jinzhu 2"}).Find(&users)
//// SELECT * FROM users WHERE name in ('jinzhu','jinzhu 2');

// LIKE
db.Where("name LIKE ?", "%jin%").Find(&users)
//// SELECT * FROM users WHERE name LIKE '%jin%';

// AND
db.Where("name = ? AND age >= ?", "jinzhu", "22").Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu' AND age >= 22;

// Time
db.Where("updated_at > ?", lastWeek).Find(&users)
//// SELECT * FROM users WHERE updated_at > '2000-01-01 00:00:00';

// BETWEEN
db.Where("created_at BETWEEN ? AND ?", lastWeek, today).Find(&users)
//// SELECT * FROM users WHERE created_at BETWEEN '2000-01-01 00:00:00' AND '2000-01-08 00:00:00';

Struct & Map查询

// Struct
db.Where(&User{Name: "jinzhu", Age: 20}).First(&user)
//// SELECT * FROM users WHERE name = "jinzhu" AND age = 20 LIMIT 1;

// Map
db.Where(map[string]interface{}{"name": "jinzhu", "age": 20}).Find(&users)
//// SELECT * FROM users WHERE name = "jinzhu" AND age = 20;

// 主键的切片
db.Where([]int64{20, 21, 22}).Find(&users)
//// SELECT * FROM users WHERE id IN (20, 21, 22);

0''false零值

db.Where(&User{Name: "jinzhu", Age: 0}).Find(&users)
//// SELECT * FROM users WHERE name = "jinzhu";

你可以使用指针或实现 Scanner/Valuer 接口来避免这个问题.

// 使用指针
type User struct {
  gorm.Model
  Name string
  Age  *int
}

// 使用 Scanner/Valuer
type User struct {
  gorm.Model
  Name string
  Age  sql.NullInt64  // sql.NullInt64 实现了 Scanner/Valuer 接口
}

Not 条件

作用与 Where 类似的情形如下：

db.Not("name", "jinzhu").First(&user)
//// SELECT * FROM users WHERE name <> "jinzhu" LIMIT 1;

// Not In
db.Not("name", []string{"jinzhu", "jinzhu 2"}).Find(&users)
//// SELECT * FROM users WHERE name NOT IN ("jinzhu", "jinzhu 2");

// Not In slice of primary keys
db.Not([]int64{1,2,3}).First(&user)
//// SELECT * FROM users WHERE id NOT IN (1,2,3);

db.Not([]int64{}).First(&user)
//// SELECT * FROM users;

// Plain SQL
db.Not("name = ?", "jinzhu").First(&user)
//// SELECT * FROM users WHERE NOT(name = "jinzhu");

// Struct
db.Not(User{Name: "jinzhu"}).First(&user)
//// SELECT * FROM users WHERE name <> "jinzhu";

Or条件

db.Where("role = ?", "admin").Or("role = ?", "super_admin").Find(&users)
//// SELECT * FROM users WHERE role = 'admin' OR role = 'super_admin';

// Struct
db.Where("name = 'jinzhu'").Or(User{Name: "jinzhu 2"}).Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2';

// Map
db.Where("name = 'jinzhu'").Or(map[string]interface{}{"name": "jinzhu 2"}).Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2';

内联条件

Where

// 根据主键获取记录 (只适用于整形主键)
db.First(&user, 23)
//// SELECT * FROM users WHERE id = 23 LIMIT 1;
// 根据主键获取记录, 如果它是一个非整形主键
db.First(&user, "id = ?", "string_primary_key")
//// SELECT * FROM users WHERE id = 'string_primary_key' LIMIT 1;

// Plain SQL
db.Find(&user, "name = ?", "jinzhu")
//// SELECT * FROM users WHERE name = "jinzhu";

db.Find(&users, "name <> ? AND age > ?", "jinzhu", 20)
//// SELECT * FROM users WHERE name <> "jinzhu" AND age > 20;

// Struct
db.Find(&users, User{Age: 20})
//// SELECT * FROM users WHERE age = 20;

// Map
db.Find(&users, map[string]interface{}{"age": 20})
//// SELECT * FROM users WHERE age = 20;

额外查询选项

// 为查询 SQL 添加额外的 SQL 操作
db.Set("gorm:query_option", "FOR UPDATE").First(&user, 10)
//// SELECT * FROM users WHERE id = 10 FOR UPDATE;

FirstOrInit

获取匹配的第一条记录，否则根据给定的条件初始化一个新的对象 (仅支持 struct 和 map 条件)

// 未找到
db.FirstOrInit(&user, User{Name: "non_existing"})
//// user -> User{Name: "non_existing"}

// 找到
db.Where(User{Name: "Jinzhu"}).FirstOrInit(&user)
//// user -> User{Id: 111, Name: "Jinzhu", Age: 20}
db.FirstOrInit(&user, map[string]interface{}{"name": "jinzhu"})
//// user -> User{Id: 111, Name: "Jinzhu", Age: 20}

Attrs

如果记录未找到，将使用参数初始化 struct.

// 未找到
db.Where(User{Name: "non_existing"}).Attrs(User{Age: 20}).FirstOrInit(&user)
//// SELECT * FROM USERS WHERE name = 'non_existing';
//// user -> User{Name: "non_existing", Age: 20}

db.Where(User{Name: "non_existing"}).Attrs("age", 20).FirstOrInit(&user)
//// SELECT * FROM USERS WHERE name = 'non_existing';
//// user -> User{Name: "non_existing", Age: 20}

// 找到
db.Where(User{Name: "Jinzhu"}).Attrs(User{Age: 30}).FirstOrInit(&user)
//// SELECT * FROM USERS WHERE name = jinzhu';
//// user -> User{Id: 111, Name: "Jinzhu", Age: 20}

Assign

不管记录是否找到，都将参数赋值给 struct.

// 未找到
db.Where(User{Name: "non_existing"}).Assign(User{Age: 20}).FirstOrInit(&user)
//// user -> User{Name: "non_existing", Age: 20}

// 找到
db.Where(User{Name: "Jinzhu"}).Assign(User{Age: 30}).FirstOrInit(&user)
//// SELECT * FROM USERS WHERE name = jinzhu';
//// user -> User{Id: 111, Name: "Jinzhu", Age: 30}

FirstOrCreate

获取匹配的第一条记录, 否则根据给定的条件创建一个新的记录 (仅支持 struct 和 map 条件)

// 未找到
db.FirstOrCreate(&user, User{Name: "non_existing"})
//// INSERT INTO "users" (name) VALUES ("non_existing");
//// user -> User{Id: 112, Name: "non_existing"}

// 找到
db.Where(User{Name: "Jinzhu"}).FirstOrCreate(&user)
//// user -> User{Id: 111, Name: "Jinzhu"}

Attrs

如果记录未找到，将使用参数创建 struct 和记录.

 // 未找到
db.Where(User{Name: "non_existing"}).Attrs(User{Age: 20}).FirstOrCreate(&user)
//// SELECT * FROM users WHERE name = 'non_existing';
//// INSERT INTO "users" (name, age) VALUES ("non_existing", 20);
//// user -> User{Id: 112, Name: "non_existing", Age: 20}

// 找到
db.Where(User{Name: "jinzhu"}).Attrs(User{Age: 30}).FirstOrCreate(&user)
//// SELECT * FROM users WHERE name = 'jinzhu';
//// user -> User{Id: 111, Name: "jinzhu", Age: 20}

Assign

不管记录是否找到，都将参数赋值给 struct 并保存至数据库.

// 未找到
db.Where(User{Name: "non_existing"}).Assign(User{Age: 20}).FirstOrCreate(&user)
//// SELECT * FROM users WHERE name = 'non_existing';
//// INSERT INTO "users" (name, age) VALUES ("non_existing", 20);
//// user -> User{Id: 112, Name: "non_existing", Age: 20}

// 找到
db.Where(User{Name: "jinzhu"}).Assign(User{Age: 30}).FirstOrCreate(&user)
//// SELECT * FROM users WHERE name = 'jinzhu';
//// UPDATE users SET age=30 WHERE id = 111;
//// user -> User{Id: 111, Name: "jinzhu", Age: 30}

高级查询

子查询

*gorm.expr

db.Where("amount > ?", db.Table("orders").Select("AVG(amount)").Where("state = ?", "paid").SubQuery()).Find(&orders)
// SELECT * FROM "orders"  WHERE "orders"."deleted_at" IS NULL AND (amount > (SELECT AVG(amount) FROM "orders"  WHERE (state = 'paid')));

选择字段

Select，指定你想从数据库中检索出的字段，默认会选择全部字段。

db.Select("name, age").Find(&users)
//// SELECT name, age FROM users;

db.Select([]string{"name", "age"}).Find(&users)
//// SELECT name, age FROM users;

db.Table("users").Select("COALESCE(age,?)", 42).Rows()
//// SELECT COALESCE(age,'42') FROM users;

排序

true

db.Order("age desc, name").Find(&users)
//// SELECT * FROM users ORDER BY age desc, name;

// 多字段排序
db.Order("age desc").Order("name").Find(&users)
//// SELECT * FROM users ORDER BY age desc, name;

// 覆盖排序
db.Order("age desc").Find(&users1).Order("age", true).Find(&users2)
//// SELECT * FROM users ORDER BY age desc; (users1)
//// SELECT * FROM users ORDER BY age; (users2)

数量

Limit，指定从数据库检索出的最大记录数。

db.Limit(3).Find(&users)
//// SELECT * FROM users LIMIT 3;

// -1 取消 Limit 条件
db.Limit(10).Find(&users1).Limit(-1).Find(&users2)
//// SELECT * FROM users LIMIT 10; (users1)
//// SELECT * FROM users; (users2)

偏移

Offset，指定开始返回记录前要跳过的记录数。

db.Offset(3).Find(&users)
//// SELECT * FROM users OFFSET 3;

// -1 取消 Offset 条件
db.Offset(10).Find(&users1).Offset(-1).Find(&users2)
//// SELECT * FROM users OFFSET 10; (users1)
//// SELECT * FROM users; (users2)

总数

Count，该 model 能获取的记录总数。

db.Where("name = ?", "jinzhu").Or("name = ?", "jinzhu 2").Find(&users).Count(&count)
//// SELECT * from USERS WHERE name = 'jinzhu' OR name = 'jinzhu 2'; (users)
//// SELECT count(*) FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2'; (count)

db.Model(&User{}).Where("name = ?", "jinzhu").Count(&count)
//// SELECT count(*) FROM users WHERE name = 'jinzhu'; (count)

db.Table("deleted_users").Count(&count)
//// SELECT count(*) FROM deleted_users;

db.Table("deleted_users").Select("count(distinct(name))").Count(&count)
//// SELECT count( distinct(name) ) FROM deleted_users; (count)

CountSELECTcount

Group & Having

rows, err := db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Rows()
for rows.Next() {
  ...
}

// 使用Scan将多条结果扫描进事先准备好的结构体切片中
type Result struct {
	Date time.Time
	Total int
}
var rets []Result
db.Table("users").Select("date(created_at) as date, sum(age) as total").Group("date(created_at)").Scan(&rets)

rows, err := db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Having("sum(amount) > ?", 100).Rows()
for rows.Next() {
  ...
}

type Result struct {
  Date  time.Time
  Total int64
}
db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Having("sum(amount) > ?", 100).Scan(&results)

连接

Joins，指定连接条件

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)

// 多连接及参数
db.Joins("JOIN emails ON emails.user_id = users.id AND emails.email = ?", "jinzhu@example.org").Joins("JOIN credit_cards ON credit_cards.user_id = users.id").Where("credit_cards.number = ?", "411111111111").Find(&user)

Pluck

Scan

var ages []int64
db.Find(&users).Pluck("age", &ages)

var names []string
db.Model(&User{}).Pluck("name", &names)

db.Table("deleted_users").Pluck("name", &names)

// 想查询多个字段？ 这样做：
db.Select("name, age").Find(&users)

扫描

Scan，扫描结果至一个 struct.

type Result struct {
  Name string
  Age  int
}

var result Result
db.Table("users").Select("name, age").Where("name = ?", "Antonio").Scan(&result)

var results []Result
db.Table("users").Select("name, age").Where("id > ?", 0).Scan(&results)

// 原生 SQL
db.Raw("SELECT name, age FROM users WHERE name = ?", "Antonio").Scan(&result)

链式操作相关

链式操作

Method Chaining，Gorm 实现了链式操作接口，所以你可以把代码写成这样：

// 创建一个查询
tx := db.Where("name = ?", "jinzhu")

// 添加更多条件
if someCondition {
  tx = tx.Where("age = ?", 20)
} else {
  tx = tx.Where("age = ?", 30)
}

if yetAnotherCondition {
  tx = tx.Where("active = ?", 1)
}

Query

立即执行方法

SQLCRUD

CreateFirstFindTakeSaveUpdateXXXDeleteScanRowRows

这有一个基于上面链式方法代码的立即执行方法的例子：

tx.Find(&user)

生成的SQL语句如下：

SELECT * FROM users where name = 'jinzhu' AND age = 30 AND active = 1;

范围

Scopes

基于它，你可以抽取一些通用逻辑，写出更多可重用的函数库。

func AmountGreaterThan1000(db *gorm.DB) *gorm.DB {
  return db.Where("amount > ?", 1000)
}

func PaidWithCreditCard(db *gorm.DB) *gorm.DB {
  return db.Where("pay_mode_sign = ?", "C")
}

func PaidWithCod(db *gorm.DB) *gorm.DB {
  return db.Where("pay_mode_sign = ?", "C")
}

func OrderStatus(status []string) func (db *gorm.DB) *gorm.DB {
  return func (db *gorm.DB) *gorm.DB {
    return db.Scopes(AmountGreaterThan1000).Where("status IN (?)", status)
  }
}

db.Scopes(AmountGreaterThan1000, PaidWithCreditCard).Find(&orders)
// 查找所有金额大于 1000 的信用卡订单

db.Scopes(AmountGreaterThan1000, PaidWithCod).Find(&orders)
// 查找所有金额大于 1000 的 COD 订单

db.Scopes(AmountGreaterThan1000, OrderStatus([]string{"paid", "shipped"})).Find(&orders)
// 查找所有金额大于 1000 且已付款或者已发货的订单

多个立即执行方法

Multiple Immediate Methods，在 GORM 中使用多个立即执行方法时，后一个立即执行方法会复用前一个立即执行方法的条件 (不包括内联条件) 。

db.Where("name LIKE ?", "jinzhu%").Find(&users, "id IN (?)", []int{1, 2, 3}).Count(&count)

生成的 Sql

SELECT * FROM users WHERE name LIKE 'jinzhu%' AND id IN (1, 2, 3)

SELECT count(*) FROM users WHERE name LIKE 'jinzhu%'

更新

更新所有字段

Save()

db.First(&user)user.Name = "七米"user.Age = 99db.Save(&user)////  UPDATE `users` SET `created_at` = '2020-02-16 12:52:20', `updated_at` = '2020-02-16 12:54:55', `deleted_at` = NULL, `name` = '七米', `age` = 99, `active` = true  WHERE `users`.`deleted_at` IS NULL AND `users`.`id` = 1

更新修改字段

UpdateUpdates

// 更新单个属性，如果它有变化
db.Model(&user).Update("name", "hello")
//// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE id=111;

// 根据给定的条件更新单个属性
db.Model(&user).Where("active = ?", true).Update("name", "hello")
//// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE id=111 AND active=true;

// 使用 map 更新多个属性，只会更新其中有变化的属性
db.Model(&user).Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})
//// UPDATE users SET name='hello', age=18, active=false, updated_at='2013-11-17 21:34:10' WHERE id=111;

// 使用 struct 更新多个属性，只会更新其中有变化且为非零值的字段
db.Model(&user).Updates(User{Name: "hello", Age: 18})
//// UPDATE users SET name='hello', age=18, updated_at = '2013-11-17 21:34:10' WHERE id = 111;

// 警告：当使用 struct 更新时，GORM只会更新那些非零值的字段
// 对于下面的操作，不会发生任何更新，"", 0, false 都是其类型的零值
db.Model(&user).Updates(User{Name: "", Age: 0, Active: false})

更新选定字段

SelectOmit

db.Model(&user).Select("name").Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})
//// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE id=111;

db.Model(&user).Omit("name").Updates(map[string]interface{}{"name": "hello", "age": 18, "active": false})
//// UPDATE users SET age=18, active=false, updated_at='2013-11-17 21:34:10' WHERE id=111;

无Hooks更新

BeforeUpdateAfterUpdateUpdatedAtAssociationsUpdateColumnUpdateColumns

// 更新单个属性，类似于 `Update`
db.Model(&user).UpdateColumn("name", "hello")
//// UPDATE users SET name='hello' WHERE id = 111;

// 更新多个属性，类似于 `Updates`
db.Model(&user).UpdateColumns(User{Name: "hello", Age: 18})
//// UPDATE users SET name='hello', age=18 WHERE id = 111;

批量更新

Hooks（钩子函数）

db.Table("users").Where("id IN (?)", []int{10, 11}).Updates(map[string]interface{}{"name": "hello", "age": 18})
//// UPDATE users SET name='hello', age=18 WHERE id IN (10, 11);

// 使用 struct 更新时，只会更新非零值字段，若想更新所有字段，请使用map[string]interface{}
db.Model(User{}).Updates(User{Name: "hello", Age: 18})
//// UPDATE users SET name='hello', age=18;

// 使用 `RowsAffected` 获取更新记录总数
db.Model(User{}).Updates(User{Name: "hello", Age: 18}).RowsAffected

使用SQL表达式更新

先查询表中的第一条数据保存至user变量。

var user User
db.First(&user)
db.Model(&user).Update("age", gorm.Expr("age * ? + ?", 2, 100))
//// UPDATE `users` SET `age` = age * 2 + 100, `updated_at` = '2020-02-16 13:10:20'  WHERE `users`.`id` = 1;

db.Model(&user).Updates(map[string]interface{}{"age": gorm.Expr("age * ? + ?", 2, 100)})
//// UPDATE "users" SET "age" = age * '2' + '100', "updated_at" = '2020-02-16 13:05:51' WHERE `users`.`id` = 1;

db.Model(&user).UpdateColumn("age", gorm.Expr("age - ?", 1))
//// UPDATE "users" SET "age" = age - 1 WHERE "id" = '1';

db.Model(&user).Where("age > 10").UpdateColumn("age", gorm.Expr("age - ?", 1))
//// UPDATE "users" SET "age" = age - 1 WHERE "id" = '1' AND quantity > 10;

修改Hooks中的值

BeforeUpdateBeforeSavescope.SetColumn

func (user *User) BeforeSave(scope *gorm.Scope) (err error) {
  if pw, err := bcrypt.GenerateFromPassword(user.Password, 0); err == nil {
    scope.SetColumn("EncryptedPassword", pw)
  }
}

其它更新选项

// 为 update SQL 添加其它的 SQL
db.Model(&user).Set("gorm:update_option", "OPTION (OPTIMIZE FOR UNKNOWN)").Update("name", "hello")
//// UPDATE users SET name='hello', updated_at = '2013-11-17 21:34:10' WHERE id=111 OPTION (OPTIMIZE FOR UNKNOWN);

删除

删除记录

警告 删除记录时，请确保主键字段有值，GORM 会通过主键去删除记录，如果主键为空，GORM 会删除该 model 的所有记录。

// 删除现有记录
db.Delete(&email)
//// DELETE from emails where id=10;

// 为删除 SQL 添加额外的 SQL 操作
db.Set("gorm:delete_option", "OPTION (OPTIMIZE FOR UNKNOWN)").Delete(&email)
//// DELETE from emails where id=10 OPTION (OPTIMIZE FOR UNKNOWN);

批量删除

删除全部匹配的记录

db.Where("email LIKE ?", "%jinzhu%").Delete(Email{})
//// DELETE from emails where email LIKE "%jinzhu%";

db.Delete(Email{}, "email LIKE ?", "%jinzhu%")
//// DELETE from emails where email LIKE "%jinzhu%";

软删除

DeletedAtDeleteDeletedAt

db.Delete(&user)
//// UPDATE users SET deleted_at="2013-10-29 10:23" WHERE id = 111;

// 批量删除
db.Where("age = ?", 20).Delete(&User{})
//// UPDATE users SET deleted_at="2013-10-29 10:23" WHERE age = 20;

// 查询记录时会忽略被软删除的记录
db.Where("age = 20").Find(&user)
//// SELECT * FROM users WHERE age = 20 AND deleted_at IS NULL;

// Unscoped 方法可以查询被软删除的记录
db.Unscoped().Where("age = 20").Find(&users)
//// SELECT * FROM users WHERE age = 20;

物理删除

// Unscoped 方法可以物理删除记录
db.Unscoped().Delete(&order)
//// DELETE FROM orders WHERE id=10;