删除

删除记录

删除记录时，被删除的值需要具有主键，否则将触发批量删除，例如

// Email's ID is `10`
db.Delete(&email)
// DELETE from emails where id = 10;

// Delete with additional conditions
db.Where("name = ?", "jinzhu").Delete(&email)
// DELETE from emails where id = 10 AND name = "jinzhu";

使用主键删除

GORM 允许使用带有内联条件的主键删除对象，它适用于数字，有关详细信息，请查看查询内联条件

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);

删除钩子

GORM 允许使用钩子 BeforeDelete、AfterDelete，这些方法将在删除记录时被调用，有关详细信息，请参阅钩子

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

指定的值没有主键值，GORM 将执行批量删除，它将删除所有匹配的记录

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%";

要有效地删除大量记录，请将包含主键的切片传递给 Delete 方法。

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

如果您在没有任何条件的情况下执行批量删除，GORM 将不会运行它，并且将返回 ErrMissingWhereClause 错误

您必须使用某些条件或使用原始 SQL 或启用 AllowGlobalUpdate 模式，例如

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

从已删除的行返回数据

返回已删除的数据，仅适用于支持 Returning 的数据库，例如

// return all columns
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}}

// return specified columns
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

如果您的模型包含 gorm.DeletedAt 字段（包含在 gorm.Model 中），它将自动获得软删除功能！

调用 Delete 时，记录不会从数据库中删除，但 GORM 会将 DeletedAt 的值设置为当前时间，并且无法再使用普通查询方法找到数据。

// 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;

如果您不想包含 gorm.Model，则可以像这样启用软删除功能

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

查找软删除的记录

您可以使用 Unscoped 查找软删除的记录

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

永久删除

您可以使用 Unscoped 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 字段的值，并且它通过插件 gorm.io/plugin/soft_delete 提供其他数据格式支持

信息 为 DeletedAt 字段创建唯一复合索引时，您必须使用其他数据格式，例如使用插件 gorm.io/plugin/soft_delete 的帮助下的 unix 秒/标志，例如

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 秒

使用 unix 秒作为删除标志

import "gorm.io/plugin/soft_delete"

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

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

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

您还可以指定使用 毫秒 或 纳秒 作为值，例如

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

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

// Delete
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"`
}

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

// Delete
UPDATE users SET is_del = 1 WHERE ID = 1;

混合模式

混合模式可以使用 0、1 或 unix 秒来标记数据是否已删除，并同时保存删除时间。

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`
}

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

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