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【GO学习】go-mysql

原作者: [db:作者] 来自: [db:来源] 收藏邀请

GORM中文文档
读者可以直接看文档，本文只是从文档记录个人常用的一些操作。

go get -u github.com/jinzhu/gorm

2.使用

官方一个快速入门的例子

package main

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

type Product struct {
    gorm.Model //嵌入常用字段
    Code string
    Price uint
}

func main() {
    db, err := gorm.Open("mysql", "root:@(localhost:3306)/golang_mysql")
    if err != nil {
        panic("failed to connect database")
    }
    //关闭数据库连接
    defer db.Close()

    //创建表
    db.AutoMigrate(&Product{})

    // 插入
    db.Create(&Product{Code: "L1212", Price: 1000})

    // 读取
    var product Product
    db.First(&product, 1) // 查询id为1的product
    db.First(&product, "code = ?", "L1212") // 查询code为l1212的product

    // 更新
    db.Model(&product).Update("Price", 2000)

    // 删除
    db.Delete(&product)
}

2.1 增

demo

package main

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

type Product struct {
    gorm.Model //嵌入常用字段
    Code string
    Price uint
}

func main() {
    db, err := gorm.Open("mysql", "root:@(localhost:3306)/golang_mysql")
    if err != nil {
        panic("failed to connect database")
    }
    //关闭数据库连接
    defer db.Close()

    //创建表
    db.AutoMigrate(&Product{})

    product := Product{Code:"No.001", Price:1000}
    fmt.Println(db.NewRecord(product)) //output: true
    db.Create(&product)
    fmt.Println(db.NewRecord(product))//output: false
}

db.NewRecord(product)用于检查主键是否为空

你可以通过 tag 定义字段的默认值，比如：

type Animal struct {
    ID   int64
    Name string `gorm:"default:'galeone'"`
    Age  int64
}

生成的 SQL 语句会排除没有值或值为零值的字段。将记录插入到数据库后，Gorm会从数据库加载那些字段的值。注意所有字段的零值, 比如 0, '', false 或者其它零值，都不会保存到数据库内，但会使用他们的默认值。

2.2 删

！！！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)

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%";

软删除
如果一个 model 有 DeletedAt 字段，他将自动获得软删除的功能！当调用 Delete 方法时，记录不会真正的从数据库中被删除，只会将DeletedAt 字段的值会被设置为当前时间

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;

2.3 查

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

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

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

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

// 查询指定的某条记录(只可在主键为整数型时使用)
db.First(&user, 10)
//// SELECT * FROM users WHERE id = 10;

Where条件

普通sql

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

// 获取全部匹配的记录
db.Where("name = ?", "jinzhu").Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu';

// <>
db.Where("name <> ?", "jinzhu").Find(&users)

// IN
db.Where("name IN (?)", []string{"jinzhu", "jinzhu 2"}).Find(&users)

// LIKE
db.Where("name LIKE ?", "%jin%").Find(&users)

// AND
db.Where("name = ? AND age >= ?", "jinzhu", "22").Find(&users)

// 时间
db.Where("updated_at > ?", lastWeek).Find(&users)

// BETWEEN
db.Where("created_at BETWEEN ? AND ?", lastWeek, today).Find(&users)

2.AND (Struct & Map)

// 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);

3.Not 条件

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";

4.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';

高级查询
1.SubQuery 子查询

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

2.选择字段

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;

3.排序

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)

4.数量

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)

5.偏移

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)

6.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;

7.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() {
    ...
}
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)

7.连接

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 = ?", "[email protected]").Joins("JOIN credit_cards ON credit_cards.user_id = users.id").Where("credit_cards.number = ?", "411111111111").Find(&user)

8.Pluck
Pluck，查询 model 中的一个列作为切片，如果您想要查询多个列，您应该使用 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)

9.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 = ?", 3).Scan(&result)

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

2.4 改

更新所有字段

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;

更新修改字段

// 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, "actived": false})
//// UPDATE users SET name='hello', age=18, actived=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, Actived: false})

3.事务

GORM 默认会将单个的 create, update, delete操作封装在事务内进行处理，以确保数据的完整性。
如果你想把多个 create, update, delete 操作作为一个原子操作，Transaction 就是用来完成这个的。

// 开启事务
tx := db.Begin()

// 在事务中执行具体的数据库操作 (事务内的操作使用 'tx' 执行，而不是 'db')
tx.Create(...)

// ...

// 如果发生错误则执行回滚
tx.Rollback()

// 或者（未发生错误时）提交事务
tx.Commit()