删除

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 批量删除，例如：

Generics API

ctx := context.Background()

// Delete by ID
err := gorm.G[Email](db).Where("id = ?", 10).Delete(ctx)
// DELETE from emails where id = 10;

// Delete with additional conditions
err := gorm.G[Email](db).Where("id = ? AND name = ?", 10, "jinzhu").Delete(ctx)
// DELETE from emails where id = 10 AND name = "jinzhu";

Traditional API

// 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";

根据主键删除

GORM 允许通过主键(可以是复合主键)和内联条件来删除对象，它可以使用数字（如以下例子。也可以使用字符串——译者注）。查看 查询-内联条件（Query Inline Conditions） 了解详情。

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);

钩子函数

对于删除操作，GORM 支持 BeforeDelete、AfterDelete Hook，在删除记录时会调用这些方法，查看 Hook 获取详情

func (u *User) BeforeDelete(tx *gorm.DB) (err error) {
    if u.Role == "admin" {
        return errors.New("admin user not allowed to delete")
    }
    return
}

批量删除

如果指定的值不包括主属性，那么 GORM 会执行批量删除，它将删除所有匹配的记录

Generics API

ctx := context.Background()

// Batch delete with conditions
err := gorm.G[Email](db).Where("email LIKE ?", "%jinzhu%").Delete(ctx)
// DELETE from emails where email LIKE "%jinzhu%";

Traditional API

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%";

可以将一个主键切片传递给Delete 方法，以便更高效的删除数据量大的记录

var users = []User{{ID: 1}, {ID: 2}, {ID: 3}}
db.Delete(&users)
// DELETE FROM users WHERE id IN (1,2,3);

db.Delete(&users, "name LIKE ?", "%jinzhu%")
// DELETE FROM users WHERE name LIKE "%jinzhu%" AND id IN (1,2,3); 

阻止全局删除

当你试图执行不带任何条件的批量删除时，GORM将不会运行并返回ErrMissingWhereClause 错误

如果一定要这么做，你必须添加一些条件，或者使用原生SQL，或者开启AllowGlobalUpdate 模式，如下例：

Generics API

ctx := context.Background()

// These will return error
err := gorm.G[User](db).Delete(ctx) // gorm.ErrMissingWhereClause

// These will work
err := gorm.G[User](db).Where("1 = 1").Delete(ctx)
// DELETE FROM `users` WHERE 1=1

Traditional API

db.Delete(&User{}).Error // gorm.ErrMissingWhereClause

db.Delete(&[]User{{Name: "jinzhu1"}, {Name: "jinzhu2"}}).Error // gorm.ErrMissingWhereClause

db.Where("1 = 1").Delete(&User{})
// DELETE FROM `users` WHERE 1=1

db.Exec("DELETE FROM users")
// DELETE FROM users

db.Session(&gorm.Session{AllowGlobalUpdate: true}).Delete(&User{})
// DELETE FROM users

返回删除行的数据

返回被删除的数据，仅当数据库支持回写功能时才能正常运行，如下例：

// 回写所有的列
var users []User
DB.Clauses(clause.Returning{}).Where("role = ?", "admin").Delete(&users)
// DELETE FROM `users` WHERE role = "admin" RETURNING *
// users => []User{{ID: 1, Name: "jinzhu", Role: "admin", Salary: 100}, {ID: 2, Name: "jinzhu.2", Role: "admin", Salary: 1000}}

// 回写指定的列
DB.Clauses(clause.Returning{Columns: []clause.Column{{Name: "name"}, {Name: "salary"}}}).Where("role = ?", "admin").Delete(&users)
// DELETE FROM `users` WHERE role = "admin" RETURNING `name`, `salary`
// users => []User{{ID: 0, Name: "jinzhu", Role: "", Salary: 100}, {ID: 0, Name: "jinzhu.2", Role: "", Salary: 1000}}

软删除

如果你的模型包含了 gorm.DeletedAt字段（该字段也被包含在gorm.Model中），那么该模型将会自动获得软删除的能力！

当调用Delete时，GORM并不会从数据库中删除该记录，而是将该记录的DeleteAt设置为当前时间，而后的一般查询方法将无法查找到此条记录。

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

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

// Soft deleted records will be ignored when querying
db.Where("age = 20").Find(&user)
// SELECT * FROM users WHERE age = 20 AND deleted_at IS NULL;

如果你并不想嵌套gorm.Model，你也可以像下方例子那样开启软删除特性：

type User struct {
  ID      int
  Deleted gorm.DeletedAt
  Name    string
}

查找被软删除的记录

你可以使用Unscoped来查询到被软删除的记录

db.Unscoped().Where("age = 20").Find(&users)
// SELECT * FROM users WHERE age = 20;

永久删除

你可以使用 Unscoped来永久删除匹配的记录

db.Unscoped().Delete(&order)
// DELETE FROM orders WHERE id=10;

删除标志

默认情况下，gorm.Model使用*time.Time作为DeletedAt 的字段类型，不过软删除插件gorm.io/plugin/soft_delete同时也提供其他的数据格式支持

提示 当使用DeletedAt创建唯一复合索引时，你必须使用其他的数据类型，例如通过gorm.io/plugin/soft_delete插件将字段类型定义为unix时间戳等等

import "gorm.io/plugin/soft_delete"

type User struct {
  ID        uint
  Name      string                `gorm:"uniqueIndex:udx_name"`
  DeletedAt soft_delete.DeletedAt `gorm:"uniqueIndex:udx_name"`
}

Unix 时间戳

使用unix时间戳作为删除标志

import "gorm.io/plugin/soft_delete"

type User struct {
  ID        uint
  Name      string
  DeletedAt soft_delete.DeletedAt
}

// 查询
SELECT * FROM users WHERE deleted_at = 0;

// 软删除
UPDATE users SET deleted_at = /* current unix second */ WHERE ID = 1;

你同样可以指定使用毫秒 milli或纳秒 nano作为值，如下例：

type User struct {
  ID    uint
  Name  string
  DeletedAt soft_delete.DeletedAt `gorm:"softDelete:milli"`
  // DeletedAt soft_delete.DeletedAt `gorm:"softDelete:nano"`
}

// 查询
SELECT * FROM users WHERE deleted_at = 0;

// 软删除
UPDATE users SET deleted_at = /* current unix milli second or nano second */ WHERE ID = 1;

使用 1 / 0 作为 删除标志

import "gorm.io/plugin/soft_delete"

type User struct {
  ID    uint
  Name  string
  IsDel soft_delete.DeletedAt `gorm:"softDelete:flag"`
}

// 查询
SELECT * FROM users WHERE is_del = 0;

// 软删除
UPDATE users SET is_del = 1 WHERE ID = 1;

混合模式

混合模式可以使用 0，1或者unix时间戳来标记数据是否被软删除，并同时可以保存被删除时间

type User struct {
  ID        uint
  Name      string
  DeletedAt time.Time
  IsDel     soft_delete.DeletedAt `gorm:"softDelete:flag,DeletedAtField:DeletedAt"` // use `1` `0`
  // IsDel     soft_delete.DeletedAt `gorm:"softDelete:,DeletedAtField:DeletedAt"` // use `unix second`
  // IsDel     soft_delete.DeletedAt `gorm:"softDelete:nano,DeletedAtField:DeletedAt"` // use `unix nano second`
}

// 查询
SELECT * FROM users WHERE is_del = 0;

// 软删除
UPDATE users SET is_del = 1, deleted_at = /* current unix second */ WHERE ID = 1;