1. 按主键删除

1.1 使用

• 说明
  如果指定的不是主键，则会触发批量删除，但是没有Where的批量删除被gorm禁止。
• 样例

db.Delete(&User{ID: 2})

或写做

db.Delete(&User{ID: 2},2)

1.2 完整示例

删除id=2 的一行

package main

import (
    "database/sql"
    "fmt"
    "gorm.io/driver/mysql"
    "gorm.io/gorm"
    "time"
)

type User struct {
    ID int64
    Age int64
    Name string
    Email string
    Company string
}


func main() {
    db,sqlDB,_ := connect()
    defer sqlDB.Close()
    db.Delete(&User{ID: 2})
}



func connect() (db *gorm.DB,sqlDB *sql.DB,err error) {
    dsn := "root:40010355@tcp(127.0.0.1:3306)/crow?charset=utf8&parseTime=True&loc=Local"
    db, err = gorm.Open(mysql.Open(dsn), &gorm.Config{})
    sqlDB,_ = db.DB()
    if err != nil {
        fmt.Printf(err.Error())
        defer sqlDB.Close()
    }else {
        fmt.Printf("OK\n")
        sqlDB.SetMaxIdleConns(10)
        sqlDB.SetMaxOpenConns(100)
        sqlDB.SetConnMaxLifetime(time.Hour)
    }
    return
}

2. 非主键删除

2.1 使用

db.Where("name LIKE ?", "%Guan%").Delete(&User{})

或写作

db.Delete(User{},"name LIKE ?","%Guan%")

2.2 示例

• 表中原有数据

mysql> select * from users ;
+----+------------+------+
| id | name       | age  |
+----+------------+------+
|  1 | LiuBei     |   28 |
|  2 | GuanYu     |   22 |
|  3 | ZhangFei   |   20 |
|  4 | ZhaoYun    |   18 |
|  5 | ZhuGeLiang |   20 |
|  6 | GuanPing   |    3 |
+----+------------+------+
6 rows in set (0.00 sec)

• 代码

上例main函数修改如下：

func main() {
    db,sqlDB,_ := connect()
    defer sqlDB.Close()

    result := db.Where("name LIKE ?", "%Guan%").Delete(&User{}).RowsAffected
    fmt.Println(result)
}

• 表修改后

mysql> select * from users ;
+----+------------+------+
| id | name       | age  |
+----+------------+------+
|  1 | LiuBei     |   28 |
|  3 | ZhangFei   |   20 |
|  4 | ZhaoYun    |   18 |
|  5 | ZhuGeLiang |   20 |
+----+------------+------+
4 rows in set (0.00 sec)

如上，关家将都被删除

3. 全局删除

gorm禁止全局删除，如果要全局删除，可以

• 指定一些条件

db.Where("1 = 1").Delete(&User{})

• 使用原生sql

db.Exec("DELETE FROM users")

4. 软删除

4.1 使用

• 说明
  实际是给deleted列加了一个删除时间
  deleted列必须存在，模型中必须有成员 Deleted 且类型为 gorm.DeletedAt，否则直接删除。
• 定义模型

模型中必须有成员 Deleted

type User struct {
    ID int64
    Age int64
    Name string
    Email string
    Company string
    Deleted gorm.DeletedAt
}

• 删除的代码

删除的代码和普通删除没有差别

db.Delete(&User{ID: 2})

4.2 完整示例

• 原有表

mysql> select * from users;
+----+----------+------+--------------------+---------+---------+
| id | name     | age  | email              | company | deleted |
+----+----------+------+--------------------+---------+---------+
|  1 | LiuBei   |   28 | liubei@xishu.com   | shu     | NULL    |
|  2 | GuanYu   |   22 | guanyu@xishu.com   | shu     | NULL    |
|  3 | ZhangFei |   20 | zhangfei@xishu.com | shu     | NULL    |
+----+----------+------+--------------------+---------+---------+
3 rows in set (0.00 sec)

• 代码

package main

import (
    "database/sql"
    "fmt"
    "gorm.io/driver/mysql"
    "gorm.io/gorm"
    "time"
)

type User struct {
    ID int64
    Age int64
    Name string
    Email string
    Company string
    Deleted gorm.DeletedAt
}


func main() {
    db,sqlDB,_ := connect()
    defer sqlDB.Close()

    db.Delete(&User{ID: 1})
}



func connect() (db *gorm.DB,sqlDB *sql.DB,err error) {
    dsn := "root:40010355@tcp(127.0.0.1:3306)/crow?charset=utf8&parseTime=True&loc=Local"
    db, err = gorm.Open(mysql.Open(dsn), &gorm.Config{})
    sqlDB,_ = db.DB()
    if err != nil {
        fmt.Printf(err.Error())
        defer sqlDB.Close()
    }else {
        fmt.Printf("OK\n")
        sqlDB.SetMaxIdleConns(10)
        sqlDB.SetMaxOpenConns(100)
        sqlDB.SetConnMaxLifetime(time.Hour)
    }
    return
}

• 表结果

mysql> select * from users;
+----+----------+------+--------------------+---------+---------------------+
| id | name     | age  | email              | company | deleted             |
+----+----------+------+--------------------+---------+---------------------+
|  1 | LiuBei   |   28 | liubei@xishu.com   | shu     | 2022-02-13 19:22:31 |
|  2 | GuanYu   |   22 | guanyu@xishu.com   | shu     | NULL                |
|  3 | ZhangFei |   20 | zhangfei@xishu.com | shu     | NULL                |
+----+----------+------+--------------------+---------+---------------------+
3 rows in set (0.00 sec)

4.3 软删除查询

4.2.1 说明

• 软删除的行，使用gorm查询时是查不到的
• 需要用Unscoped()查询软删除数据

db.Unscoped().Find(&users)

• 彻底删除软删除数据

db.Unscoped().Delete(&User{ID: 1})

4.3.2 示例

• gorm 直接查询查不到软删除

func main() {
    db,sqlDB,_ := connect()
    defer sqlDB.Close()
    var users []User
    db.Find(&users)
    fmt.Println(users)
}

输出

OK
[{2 22 GuanYu guanyu@xishu.com shu {0001-01-01 00:00:00 +0000 UTC false}} {3 20 ZhangFei zhangfei@xishu.com shu {0001-01-01 00:00:00 +0000 UTC false}}]

• 使用Unscoped()查询

func main() {
    db,sqlDB,_ := connect()
    defer sqlDB.Close()
    var users []User
    db.Unscoped().Find(&users)
    fmt.Println(users)
}

结果

如下：可以查到软删除的刘备信息

OK
[{1 28 LiuBei liubei@xishu.com shu {2022-02-13 19:22:31 +0800 CST true}} {2 22 GuanYu guanyu@xishu.com shu {0001-01-01 00:00:00 +0000 UTC false}} {3 20 ZhangFei zhangfei@xishu.com shu {0001-01-01 00:00:00 +0000 UTC false}}]

• 彻底删除被软删除数据

func main() {
    db,sqlDB,_ := connect()
    defer sqlDB.Close()
    var users []User
    db.Unscoped().Delete(&User{ID: 1})
    fmt.Println(users)
}