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:

  1. // 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 allows to delete objects using primary key(s) with inline condition, it works with numbers, check out Query Inline Conditions for details

  1. 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

  1. 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

  1. 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:

  1. 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

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,记录不会被从数据库中真正删除。但 GORM 会将 DeletedAt 置为当前时间, 并且你不能再通过正常的查询方法找到该记录。

  1. // 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:

  1. 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

  1. 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

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

Delete Flag

将 unix 时间戳作为 delete flag

  1. 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 = /* current unix second */ WHERE ID = 1;

INFO 在配合 unique 字段使用软删除时,您需要使用这个基于 unix 时间戳的 DeletedAt 字段创建一个复合索引,例如:

  1. 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"`
    }

使用 1 / 0 作为 delete flag

  1. 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;

最后更新于 2021-06-14