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 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";

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);

Delete Hook

对于删除操作,GORM 支持 BeforeDeleteAfterDelete 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

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%";

阻止全局删除

如果在没有任何条件的情况下执行批量删除,GORM 不会执行该操作,并返回 ErrMissingWhereClause 错误

对此,你必须加一些条件,或者使用原生 SQL,或者启用 AllowGlobalUpdate 模式,例如:

db.Delete(&User{}).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,仅适用于支持 Returning 的数据库,例如:

// 返回所有列
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}}

// 返回指定的列
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

如果您的模型包含了一个 gorm.deletedat 字段(gorm.Model 已经包含了该字段),它将自动获得软删除的能力!

拥有软删除能力的模型调用 Delete 时,记录不会从数据库中被真正删除。但 GORM 会将 DeletedAt 置为当前时间, 并且你不能再通过普通的查询方法找到该记录。

// user 的 ID 是 `111`
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;

// 在查询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;

如果您不想引入 gorm.Model,您也可以这样启用软删除特性:

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

查找被软删除的记录

您可以使用 Unscoped 找到被软删除的记录

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

永久删除

您也可以使用 Unscoped 永久删除匹配的记录

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

Delete Flag

默认情况下,gorm.Model 使用 *time.Time 作为 DeletedAt 字段的值。此外,通过 gorm.io/plugin/soft_delete 插件还支持其它数据格式。

提示 当使用 DeletedAt 字段创建唯一复合索引时,你必须通过 gorm.io/plugin/soft_delete 等插件将字段定义为时间戳之类的数据格式,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 时间戳

将 unix 秒级时间戳作为 delete flag

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;

// 删除
UPDATE users SET deleted_at = /* 当前时间戳 */ WHERE ID = 1;

你还可以指定 millinano 使用毫秒、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"`
}

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

// 删除
UPDATE users SET deleted_at = /* 当前毫秒、纳秒时间戳 */ WHERE ID = 1;

使用 1 / 0 作为 Delete Flag

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;

// 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 unix 秒来标识数据是否已被删除,并同时保存删除的时间。

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

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

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

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