GoWeb开发-2.gorm操作MySQL

1.安装gorm

go get -u gorm.io/gorm
go get -u gorm.io/driver/mysql

2.链接MySQL

import (
	"gorm.io/driver/mysql"
	"gorm.io/gorm"
)

type Todo struct {
    
    
	ID int `json:"id"`
	Title string `json:"title"`
	Status bool `json:"status"`
}

	dsn := "root:root@tcp(127.0.0.1:3306)/test?charset=utf8mb4&parseTime=True&loc=Local"
	db, err := gorm.Open(mysql.Open(dsn), &gorm.Config{
    
    })
	if err!=nil {
    
    
		panic(err)
	}
	//创建表
	//db.AutoMigrate(&Todo{})

MySQl 驱动程序提供了一些高级配置可以在初始化过程中使用，例如：

db, err := gorm.Open(mysql.New(mysql.Config{
    
    
  DSN: "gorm:gorm@tcp(127.0.0.1:3306)/gorm?charset=utf8&parseTime=True&loc=Local", // DSN data source name
  DefaultStringSize: 256, // string 类型字段的默认长度
  DisableDatetimePrecision: true, // 禁用 datetime 精度，MySQL 5.6 之前的数据库不支持
  DontSupportRenameIndex: true, // 重命名索引时采用删除并新建的方式，MySQL 5.7 之前的数据库和 MariaDB 不支持重命名索引
  DontSupportRenameColumn: true, // 用 `change` 重命名列，MySQL 8 之前的数据库和 MariaDB 不支持重命名列
  SkipInitializeWithVersion: false, // 根据当前 MySQL 版本自动配置
}), &gorm.Config{
    
    })

3.添加数据

user := User{
    
    Name: "Jinzhu", Age: 18, Birthday: time.Now()}
result := db.Create(&user) // 通过数据的指针来创建
user.ID             // 返回插入数据的主键
result.Error        // 返回 error
result.RowsAffected // 返回插入记录的条数

用指定的字段创建记录

//创建记录并更新给出的字段。
db.Select("Name", "Age", "CreatedAt").Create(&user)
// INSERT INTO `users` (`name`,`age`,`created_at`) VALUES ("jinzhu", 18, "2020-07-04 11:05:21.775")
//创建一个记录且一同忽略传递给略去的字段值。
db.Omit("Name", "Age", "CreatedAt").Create(&user)
// INSERT INTO `users` (`birthday`,`updated_at`) VALUES ("2020-01-01 00:00:00.000", "2020-07-04 11:05:21.775")

批量插入

var users = []User{
    
    {
    
    Name: "jinzhu1"}, {
    
    Name: "jinzhu2"}, {
    
    Name: "jinzhu3"}}
db.Create(&users)

for _, user := range users {
    
    
  user.ID // 1,2,3
}

根据 Map 创建

db.Model(&User{
    
    }).Create(map[string]interface{
    
    }{
    
    
  "Name": "jinzhu", "Age": 18,
})

// batch insert from `[]map[string]interface{}{}`
db.Model(&User{
    
    }).Create([]map[string]interface{
    
    }{
    
    
  {
    
    "Name": "jinzhu_1", "Age": 18},
  {
    
    "Name": "jinzhu_2", "Age": 20},
})

4.查询数据

检索单个对象

// 获取第一条记录（主键升序）
db.First(&user)
// SELECT * FROM users ORDER BY id LIMIT 1;

// 获取一条记录，没有指定排序字段
db.Take(&user)
// SELECT * FROM users LIMIT 1;

// 获取最后一条记录（主键降序）
db.Last(&user)
// SELECT * FROM users ORDER BY id DESC LIMIT 1;

result := db.First(&user)
result.RowsAffected // 返回找到的记录数
result.Error        // returns error or nil

// 检查 ErrRecordNotFound 错误
errors.Is(result.Error, gorm.ErrRecordNotFound)

用主键检索

db.First(&user, 10)
// SELECT * FROM users WHERE id = 10;

db.First(&user, "10")
// SELECT * FROM users WHERE id = 10;

db.Find(&users, []int{
    
    1,2,3})
// SELECT * FROM users WHERE id IN (1,2,3);

检索全部对象

// 获取全部记录
result := db.Find(&users)
// SELECT * FROM users;

result.RowsAffected // 返回找到的记录数，相当于 `len(users)`
result.Error        // returns error

条件

// 获取第一条匹配的记录
db.Where("name = ?", "jinzhu").First(&user)
// SELECT * FROM users WHERE name = 'jinzhu' ORDER BY id LIMIT 1;

// 获取全部匹配的记录
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
db.Where(&User{
    
    Name: "jinzhu", Age: 20}).First(&user)
// SELECT * FROM users WHERE name = "jinzhu" AND age = 20 ORDER BY id LIMIT 1;

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

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

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

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

// 根据主键获取记录，如果是非整型主键
db.First(&user, "id = ?", "string_primary_key")
// SELECT * FROM users WHERE id = 'string_primary_key';

// 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;

db.Not("name = ?", "jinzhu").First(&user)
// SELECT * FROM users WHERE NOT name = "jinzhu" ORDER BY id LIMIT 1;

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

// Struct
db.Not(User{
    
    Name: "jinzhu", Age: 18}).First(&user)
// SELECT * FROM users WHERE name <> "jinzhu" AND age <> 18 ORDER BY id LIMIT 1;

// 不在主键切片中的记录
db.Not([]int64{
    
    1,2,3}).First(&user)
// SELECT * FROM users WHERE id NOT IN (1,2,3) ORDER BY id LIMIT 1;

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", Age: 18}).Find(&users)
// SELECT * FROM users WHERE name = 'jinzhu' OR (name = 'jinzhu 2' AND age = 18);

// Map
db.Where("name = 'jinzhu'").Or(map[string]interface{
    
    }{
    
    "name": "jinzhu 2", "age": 18}).Find(&users)
// SELECT * FROM users WHERE name = 'jinzhu' OR (name = 'jinzhu 2' AND age = 18);


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;

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

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

db.Clauses(clause.OrderBy{
    
    
  Expression: clause.Expr{
    
    SQL: "FIELD(id,?)", Vars: []interface{
    
    }{
    
    []int{
    
    1, 2, 3}}, WithoutParentheses: true},
}).Find(&User{
    
    })
// SELECT * FROM users ORDER BY FIELD(id,1,2,3)

//Limit 指定获取记录的最大数量 Offset 指定在开始返回记录之前要跳过的记录数量
db.Limit(3).Find(&users)
// SELECT * FROM users LIMIT 3;

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

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

db.Limit(10).Offset(5).Find(&users)
// SELECT * FROM users OFFSET 5 LIMIT 10;

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

type result struct {
    
    
  Date  time.Time
  Total int
}

db.Model(&User{
    
    }).Select("name, sum(age) as total").Where("name LIKE ?", "group%").Group("name").First(&result)
// SELECT name, sum(age) as total FROM `users` WHERE name LIKE "group%" GROUP BY `name` LIMIT 1


db.Model(&User{
    
    }).Select("name, sum(age) as total").Group("name").Having("name = ?", "group").Find(&result)
// SELECT name, sum(age) as total FROM `users` GROUP BY `name` HAVING name = "group"

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

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)

5.更新数据

保存所有字段

db.First(&user)

user.Name = "jinzhu 2"
user.Age = 100
db.Save(&user)
// UPDATE users SET name='jinzhu 2', age=100, birthday='2016-01-01', updated_at = '2013-11-17 21:34:10' WHERE id=111;

更新单个列

// 条件更新
db.Model(&User{
    
    }).Where("active = ?", true).Update("name", "hello")
// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE active=true;

// User 的 ID 是 `111`
db.Model(&user).Update("name", "hello")
// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE id=111;

// 根据条件和 model 的值进行更新
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;

更新多列

// 根据 `struct` 更新属性，只会更新非零值的字段
db.Model(&user).Updates(User{
    
    Name: "hello", Age: 18, Active: false})
// UPDATE users SET name='hello', age=18, updated_at = '2013-11-17 21:34:10' WHERE id = 111;

// 根据 `map` 更新属性
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;

更新选定字段

// 使用 Map 进行 Select
// User's ID is `111`:
db.Model(&user).Select("name").Updates(map[string]interface{
    
    }{
    
    "name": "hello", "age": 18, "active": false})
// UPDATE users SET name='hello' 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;

// 使用 Struct 进行 Select（会 select 零值的字段）
db.Model(&user).Select("Name", "Age").Updates(User{
    
    Name: "new_name", Age: 0})
// UPDATE users SET name='new_name', age=0 WHERE id=111;

// Select 所有字段（查询包括零值字段的所有字段）
db.Model(&user).Select("*").Update(User{
    
    Name: "jinzhu", Role: "admin", Age: 0})

// Select 除 Role 外的所有字段（包括零值字段的所有字段）
db.Model(&user).Select("*").Omit("Role").Update(User{
    
    Name: "jinzhu", Role: "admin", Age: 0})

6.删除数据

删除一条记录
删除一条记录时，删除对象需要指定主键，否则会触发批量 Delete，例如：

// Email 的 ID 是 `10`
db.Delete(&email)
// DELETE from emails where id = 10;

// 带额外条件的删除
db.Where("name = ?", "jinzhu").Delete(&email)
// DELETE from emails where id = 10 AND name = "jinzhu";

db.Delete(&User{
    
    }, 10)
// DELETE FROM users WHERE id = 10;

db.Delete(&User{
    
    }, "10")
// DELETE FROM users WHERE id = 10;

db.Delete(&users, []int{
    
    1,2,3})
// DELETE FROM users WHERE id IN (1,2,3);

批量删除

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%";

7.原生sql

type Result struct {
    
    
  ID   int
  Name string
  Age  int
}

var result Result
db.Raw("SELECT id, name, age FROM users WHERE name = ?", 3).Scan(&result)

db.Raw("SELECT id, name, age FROM users WHERE name = ?", 3).Scan(&result)

var age int
db.Raw("SELECT SUM(age) FROM users WHERE role = ?", "admin").Scan(&age)

var users []User
db.Raw("UPDATE users SET name = ? WHERE age = ? RETURNING id, name", "jinzhu", 20).Scan(&users)


db.Exec("DROP TABLE users")
db.Exec("UPDATE orders SET shipped_at = ? WHERE id IN ?", time.Now(), []int64{
    
    1, 2, 3})

// Exec with SQL Expression
db.Exec("UPDATE users SET money = ? WHERE name = ?", gorm.Expr("money * ? + ?", 10000, 1), "jinzhu")

GoWeb开发-2.gorm操作MySQL

1.安装gorm

2.链接MySQL

3.添加数据

4.查询数据

5.更新数据

6.删除数据

7.原生sql

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