golang gorm的预加载及软删硬删的数据操作示例

Dulcea ·

更新时间:2024-11-13

· 1842 次阅读

1. orm读写数据

1. 创建

1.1. 创建记录

1.2. 默认值

1.3. 在Callbacks中设置主键

1.4. 扩展创建选项

2. 查询

2.1. Where查询条件 (简单SQL)

2.2. Where查询条件 (Struct & Map)

2.3. Not条件查询

2.4. 带内联条件的查询

2.5. Or条件查询

2.6. 查询链

2.7. 扩展查询选项

2.8. FirstOrInit

2.9. Attrs

2.10. Assign

2.11. FirstOrCreate

2.12. Attrs

2.13. Assign

2.14. Select

2.15. Order

2.16. Limit

2.17. Offset

2.18. Count

2.19. Group & Having

2.20. Join

2.21. Pluck

2.22. Scan

2.23. Scopes

2.24. 指定表名

3. 预加载

3.1. 自定义预加载SQL

3.2. 嵌套预加载

4. 更新

4.1. 更新全部字段

4.2. 更新更改字段

4.3. 更新选择的字段

4.4. 更新更改字段但不进行Callbacks

4.5. Batch Updates 批量更新

4.6. 使用SQL表达式更新

4.7. 在Callbacks中更改更新值

4.8. 额外更新选项

5. 删除/软删除

5.1. 批量删除

5.2. 软删除

6. 关联

6.1. 创建/更新时跳过保存关联

6.2. tag设置跳过保存关联

1. orm读写数据 1. 创建 1.1. 创建记录

user := User{Name: "Jinzhu", Age: 18, Birthday: time.Now()}
db.NewRecord(user) // => 主键为空返回`true`
db.Create(&user)
db.NewRecord(user) // => 创建`user`后返回`false`

1.2. 默认值

您可以在gorm tag中定义默认值，然后插入SQL将忽略具有默认值的这些字段，并且其值为空，并且在将记录插入数据库后，gorm将从数据库加载这些字段的值。

type Animal struct {
    ID   int64
    Name string `gorm:"default:'galeone'"`
    Age  int64
}
var animal = Animal{Age: 99, Name: ""}
db.Create(&animal)
// INSERT INTO animals("age") values('99');
// SELECT name from animals WHERE ID=111; // 返回主键为 111
// animal.Name => 'galeone'

1.3. 在Callbacks中设置主键

如果要在BeforeCreate回调中设置主字段的值，可以使用scope.SetColumn，例如：

func (user *User) BeforeCreate(scope *gorm.Scope) error {
  scope.SetColumn("ID", uuid.New())
  return nil
}

1.4. 扩展创建选项

// 为Instert语句添加扩展SQL选项
db.Set("gorm:insert_option", "ON CONFLICT").Create(&amp;product)
// INSERT INTO products (name, code) VALUES ("name", "code") ON CONFLICT;

2. 查询

// 获取第一条记录，按主键排序
db.First(&user)
//// SELECT * FROM users ORDER BY id LIMIT 1;
// 获取最后一条记录，按主键排序
db.Last(&user)
//// SELECT * FROM users ORDER BY id DESC LIMIT 1;
// 获取所有记录
db.Find(&users)
//// SELECT * FROM users;
// 使用主键获取记录
db.First(&user, 10)
//// SELECT * FROM users WHERE id = 10;

2.1. Where查询条件 (简单SQL)

// 获取第一个匹配记录
db.Where("name = ?", "jinzhu").First(&user)
//// SELECT * FROM users WHERE name = 'jinzhu' limit 1;
// 获取所有匹配记录
db.Where("name = ?", "jinzhu").Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu';
db.Where("name <> ?", "jinzhu").Find(&users)
// IN
db.Where("name in (?)", []string{"jinzhu", "jinzhu 2"}).Find(&users)
// LIKE
db.Where("name LIKE ?", "%jin%").Find(&users)
// AND
db.Where("name = ? AND age >= ?", "jinzhu", "22").Find(&users)
// Time
db.Where("updated_at > ?", lastWeek).Find(&users)
db.Where("created_at BETWEEN ? AND ?", lastWeek, today).Find(&users)

2.2. Where查询条件 (Struct & Map)

注意：当使用struct查询时，GORM将只查询那些具有值的字段

// Struct
db.Where(&User{Name: "jinzhu", Age: 20}).First(&user)
//// SELECT * FROM users WHERE name = "jinzhu" AND age = 20 LIMIT 1;
// Map
db.Where(map[string]interface{}{"name": "jinzhu", "age": 20}).Find(&users)
//// SELECT * FROM users WHERE name = "jinzhu" AND age = 20;
// 主键的Slice
db.Where([]int64{20, 21, 22}).Find(&users)
//// SELECT * FROM users WHERE id IN (20, 21, 22);

2.3. Not条件查询

db.Not("name", "jinzhu").First(&user)
//// SELECT * FROM users WHERE name <> "jinzhu" LIMIT 1;
// Not In
db.Not("name", []string{"jinzhu", "jinzhu 2"}).Find(&users)
//// SELECT * FROM users WHERE name NOT IN ("jinzhu", "jinzhu 2");
// Not In slice of primary keys
db.Not([]int64{1,2,3}).First(&user)
//// SELECT * FROM users WHERE id NOT IN (1,2,3);
db.Not([]int64{}).First(&user)
//// SELECT * FROM users;
// Plain SQL
db.Not("name = ?", "jinzhu").First(&user)
//// SELECT * FROM users WHERE NOT(name = "jinzhu");
// Struct
db.Not(User{Name: "jinzhu"}).First(&user)
//// SELECT * FROM users WHERE name <> "jinzhu";

2.4. 带内联条件的查询

注意：使用主键查询时，应仔细检查所传递的值是否为有效主键，以避免SQL注入

// 按主键获取
db.First(&user, 23)
//// SELECT * FROM users WHERE id = 23 LIMIT 1;
// 简单SQL
db.Find(&user, "name = ?", "jinzhu")
//// SELECT * FROM users WHERE name = "jinzhu";
db.Find(&users, "name <> ? AND age > ?", "jinzhu", 20)
//// SELECT * FROM users WHERE name <> "jinzhu" AND age > 20;
// Struct
db.Find(&users, User{Age: 20})
//// SELECT * FROM users WHERE age = 20;
// Map
db.Find(&users, map[string]interface{}{"age": 20})
//// SELECT * FROM users WHERE age = 20;

2.5. Or条件查询

db.Where("role = ?", "admin").Or("role = ?", "super_admin").Find(&users)
//// SELECT * FROM users WHERE role = 'admin' OR role = 'super_admin';
// Struct
db.Where("name = 'jinzhu'").Or(User{Name: "jinzhu 2"}).Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2';
// Map
db.Where("name = 'jinzhu'").Or(map[string]interface{}{"name": "jinzhu 2"}).Find(&users)

2.6. 查询链

Gorm有一个可链接的API，你可以这样使用它

db.Where("name <> ?","jinzhu").Where("age >= ? and role <> ?",20,"admin").Find(&users)
//// SELECT * FROM users WHERE name <> 'jinzhu' AND age >= 20 AND role <> 'admin';
db.Where("role = ?", "admin").Or("role = ?", "super_admin").Not("name = ?", "jinzhu").Find(&users)

2.7. 扩展查询选项

// 为Select语句添加扩展SQL选项
db.Set("gorm:query_option", "FOR UPDATE").First(&amp;user, 10)
//// SELECT * FROM users WHERE id = 10 FOR UPDATE;

2.8. FirstOrInit

获取第一个匹配的记录，或者使用给定的条件初始化一个新的记录（仅适用于struct，map条件）

// Unfound
db.FirstOrInit(&user, User{Name: "non_existing"})
//// user -> User{Name: "non_existing"}
// Found
db.Where(User{Name: "Jinzhu"}).FirstOrInit(&user)
//// user -> User{Id: 111, Name: "Jinzhu", Age: 20}
db.FirstOrInit(&user, map[string]interface{}{"name": "jinzhu"})
//// user -> User{Id: 111, Name: "Jinzhu", Age: 20}

2.9. Attrs

如果未找到记录，则使用参数初始化结构

// Unfound
db.Where(User{Name: "non_existing"}).Attrs(User{Age: 20}).FirstOrInit(&user)
//// SELECT * FROM USERS WHERE name = 'non_existing';
//// user -> User{Name: "non_existing", Age: 20}
db.Where(User{Name: "non_existing"}).Attrs("age", 20).FirstOrInit(&user)
//// SELECT * FROM USERS WHERE name = 'non_existing';
//// user -> User{Name: "non_existing", Age: 20}
// Found
db.Where(User{Name: "Jinzhu"}).Attrs(User{Age: 30}).FirstOrInit(&user)
//// SELECT * FROM USERS WHERE name = jinzhu';
//// user -> User{Id: 111, Name: "Jinzhu", Age: 20}

2.10. Assign

将参数分配给结果，不管它是否被找到

// Unfound
db.Where(User{Name: "non_existing"}).Assign(User{Age: 20}).FirstOrInit(&user)
//// user -> User{Name: "non_existing", Age: 20}
// Found
db.Where(User{Name: "Jinzhu"}).Assign(User{Age: 30}).FirstOrInit(&user)
//// SELECT * FROM USERS WHERE name = jinzhu';
//// user -> User{Id: 111, Name: "Jinzhu", Age: 30}

2.11. FirstOrCreate

获取第一个匹配的记录，或创建一个具有给定条件的新记录（仅适用于struct, map条件）

// Unfound
db.FirstOrCreate(&user, User{Name: "non_existing"})
//// INSERT INTO "users" (name) VALUES ("non_existing");
//// user -> User{Id: 112, Name: "non_existing"}
// Found
db.Where(User{Name: "Jinzhu"}).FirstOrCreate(&user)
//// user -> User{Id: 111, Name: "Jinzhu"}

2.12. Attrs

如果未找到记录，则为参数分配结构

// Unfound
db.Where(User{Name: "non_existing"}).Attrs(User{Age: 20}).FirstOrCreate(&user)
//// SELECT * FROM users WHERE name = 'non_existing';
//// INSERT INTO "users" (name, age) VALUES ("non_existing", 20);
//// user -> User{Id: 112, Name: "non_existing", Age: 20}
// Found
db.Where(User{Name: "jinzhu"}).Attrs(User{Age: 30}).FirstOrCreate(&user)
//// SELECT * FROM users WHERE name = 'jinzhu';
//// user -> User{Id: 111, Name: "jinzhu", Age: 20}

2.13. Assign

将其分配给记录，而不管它是否被找到，并保存回数据库。

// Unfound
db.Where(User{Name: "non_existing"}).Assign(User{Age: 20}).FirstOrCreate(&user)
//// SELECT * FROM users WHERE name = 'non_existing';
//// INSERT INTO "users" (name, age) VALUES ("non_existing", 20);
//// user -> User{Id: 112, Name: "non_existing", Age: 20}
// Found
db.Where(User{Name: "jinzhu"}).Assign(User{Age: 30}).FirstOrCreate(&user)
//// SELECT * FROM users WHERE name = 'jinzhu';
//// UPDATE users SET age=30 WHERE id = 111;
//// user -> User{Id: 111, Name: "jinzhu", Age: 30}

2.14. Select

指定要从数据库检索的字段，默认情况下，将选择所有字段;

db.Select("name, age").Find(&users)
//// SELECT name, age FROM users;
db.Select([]string{"name", "age"}).Find(&users)
//// SELECT name, age FROM users;
db.Table("users").Select("COALESCE(age,?)", 42).Rows()
//// SELECT COALESCE(age,'42') FROM users;

2.15. Order

在从数据库检索记录时指定顺序，将重排序设置为true以覆盖定义的条件

db.Order("age desc, name").Find(&users)
//// SELECT * FROM users ORDER BY age desc, name;
// Multiple orders
db.Order("age desc").Order("name").Find(&users)
//// SELECT * FROM users ORDER BY age desc, name;
// ReOrder
db.Order("age desc").Find(&users1).Order("age", true).Find(&users2)
//// SELECT * FROM users ORDER BY age desc; (users1)
//// SELECT * FROM users ORDER BY age; (users2)

2.16. Limit

指定要检索的记录数

db.Limit(3).Find(&users)
//// SELECT * FROM users LIMIT 3;
// Cancel limit condition with -1
db.Limit(10).Find(&users1).Limit(-1).Find(&users2)
//// SELECT * FROM users LIMIT 10; (users1)
//// SELECT * FROM users; (users2)

2.17. Offset

指定在开始返回记录之前要跳过的记录数

db.Offset(3).Find(&users)
//// SELECT * FROM users OFFSET 3;
// Cancel offset condition with -1
db.Offset(10).Find(&users1).Offset(-1).Find(&users2)
//// SELECT * FROM users OFFSET 10; (users1)
//// SELECT * FROM users; (users2)

eg:

type Info struct {
Id      int    `json:"id"`
Code    string `json:"code"`
HwCode  string `json:"hw_code"`
Name    string `json:"name"`
Des     string `json:"des"`
Created int64  `json:"created"`
Updated int64  `json:"updated"`
BrandId int    `json:"brand_id"`
}
func (Info) TableName() string {
return "bike_color"
}
func (o object) QueryInfo2(id int) *Info {
r := new(Info)
o.gDb.Where("id = ?",id).Find(&r)
return r
}
// 列表
func (o object) QueryList2(page, PageSize int) (list []Info, total int) {
o.gDb.Offset((page-1)*PageSize).Limit(PageSize).Find(&list)
total = len(list)
return
}

2.18. Count

获取模型的记录数

db.Where("name = ?", "jinzhu").Or("name = ?", "jinzhu 2").Find(&users).Count(&count)
//// SELECT * from USERS WHERE name = 'jinzhu' OR name = 'jinzhu 2'; (users)
//// SELECT count(*) FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2'; (count)
db.Model(&User{}).Where("name = ?", "jinzhu").Count(&count)
//// SELECT count(*) FROM users WHERE name = 'jinzhu'; (count)
db.Table("deleted_users").Count(&count)
//// SELECT count(*) FROM deleted_users;

2.19. Group & Having

rows, err := db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Rows()
for rows.Next() {
    ...
}
rows, err := db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Having("sum(amount) > ?", 100).Rows()
for rows.Next() {
    ...
}
type Result struct {
    Date  time.Time
    Total int64
}
db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Having("sum(amount) > ?", 100).Scan(&results)

2.20. Join

指定连接条件

rows, err := db.Table("users").Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Rows()
for rows.Next() {
    ...
}
db.Table("users").Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Scan(&results)
// 多个连接与参数
db.Joins("JOIN emails ON emails.user_id = users.id AND emails.email = ?", "jinzhu@example.org").Joins("JOIN credit_cards ON credit_cards.user_id = users.id").Where("credit_cards.number = ?", "411111111111").Find(&user)

2.21. Pluck

将模型中的单个列作为地图查询，如果要查询多个列，可以使用Scan

var ages []int64
db.Find(&users).Pluck("age", &ages)
var names []string
db.Model(&User{}).Pluck("name", &names)
db.Table("deleted_users").Pluck("name", &names)
// 要返回多个列，做这样：
db.Select("name, age").Find(&users)

2.22. Scan

将结果扫描到另一个结构中。

type Result struct {
    Name string
    Age  int
}
var result Result
db.Table("users").Select("name, age").Where("name = ?", 3).Scan(&result)
// Raw SQL
db.Raw("SELECT name, age FROM users WHERE name = ?", 3).Scan(&result)

2.23. Scopes

将当前数据库连接传递到func(*DB) *DB，可以用于动态添加条件

func AmountGreaterThan1000(db *gorm.DB) *gorm.DB {
    return db.Where("amount > ?", 1000)
}
func PaidWithCreditCard(db *gorm.DB) *gorm.DB {
    return db.Where("pay_mode_sign = ?", "C")
}
func PaidWithCod(db *gorm.DB) *gorm.DB {
    return db.Where("pay_mode_sign = ?", "C")
}
func OrderStatus(status []string) func (db *gorm.DB) *gorm.DB {
    return func (db *gorm.DB) *gorm.DB {
        return db.Scopes(AmountGreaterThan1000).Where("status in (?)", status)
    }
}
db.Scopes(AmountGreaterThan1000, PaidWithCreditCard).Find(&orders)
// 查找所有信用卡订单和金额大于1000
db.Scopes(AmountGreaterThan1000, PaidWithCod).Find(&orders)
// 查找所有COD订单和金额大于1000
db.Scopes(OrderStatus([]string{"paid", "shipped"})).Find(&orders)
// 查找所有付费，发货订单

2.24. 指定表名

// 使用User结构定义创建`deleted_users`表
db.Table("deleted_users").CreateTable(&User{})
var deleted_users []User
db.Table("deleted_users").Find(&deleted_users)
//// SELECT * FROM deleted_users;
db.Table("deleted_users").Where("name = ?", "jinzhu").Delete()
//// DELETE FROM deleted_users WHERE name = 'jinzhu';

3. 预加载

db.Preload("Orders").Find(&users)
//// SELECT * FROM users;
//// SELECT * FROM orders WHERE user_id IN (1,2,3,4);
db.Preload("Orders", "state NOT IN (?)", "cancelled").Find(&users)
//// SELECT * FROM users;
//// SELECT * FROM orders WHERE user_id IN (1,2,3,4) AND state NOT IN ('cancelled');
db.Where("state = ?", "active").Preload("Orders", "state NOT IN (?)", "cancelled").Find(&users)
//// SELECT * FROM users WHERE state = 'active';
//// SELECT * FROM orders WHERE user_id IN (1,2) AND state NOT IN ('cancelled');
db.Preload("Orders").Preload("Profile").Preload("Role").Find(&users)
//// SELECT * FROM users;
//// SELECT * FROM orders WHERE user_id IN (1,2,3,4); // has many
//// SELECT * FROM profiles WHERE user_id IN (1,2,3,4); // has one
//// SELECT * FROM roles WHERE id IN (4,5,6); // belongs to

3.1. 自定义预加载SQL

您可以通过传递func(db *gorm.DB) *gorm.DB（与Scopes的使用方法相同）来自定义预加载SQL，例如：

db.Preload("Orders", func(db *gorm.DB) *gorm.DB {
    return db.Order("orders.amount DESC")
}).Find(&amp;users)
//// SELECT * FROM users;
//// SELECT * FROM orders WHERE user_id IN (1,2,3,4) order by orders.amount DESC;

3.2. 嵌套预加载

db.Preload("Orders.OrderItems").Find(&amp;users)
db.Preload("Orders", "state = ?", "paid").Preload("Orders.OrderItems").Find(&amp;users)

4. 更新 4.1. 更新全部字段

Save将包括执行更新SQL时的所有字段，即使它没有更改

db.First(&user)
user.Name = "jinzhu 2"
user.Age = 100
db.Save(&user)
//// UPDATE users SET name='jinzhu 2', age=100, birthday='2016-01-01', updated_at = '2013-11-17 21:34:10' WHERE id=111;

4.2. 更新更改字段

如果只想更新更改的字段，可以使用Update, Updates

// 更新单个属性（如果更改）
db.Model(&user).Update("name", "hello")
//// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE id=111;
// 使用组合条件更新单个属性
db.Model(&user).Where("active = ?", true).Update("name", "hello")
//// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE id=111 AND active=true;
// 使用`map`更新多个属性，只会更新这些更改的字段
db.Model(&user).Updates(map[string]interface{}{"name": "hello", "age": 18, "actived": false})
//// UPDATE users SET name='hello', age=18, actived=false, updated_at='2013-11-17 21:34:10' WHERE id=111;
// 使用`struct`更新多个属性，只会更新这些更改的和非空白字段
db.Model(&user).Updates(User{Name: "hello", Age: 18})
//// UPDATE users SET name='hello', age=18, updated_at = '2013-11-17 21:34:10' WHERE id = 111;
// 警告:当使用struct更新时，FORM将仅更新具有非空值的字段
// 对于下面的更新，什么都不会更新为""，0，false是其类型的空白值
db.Model(&user).Updates(User{Name: "", Age: 0, Actived: false})

4.3. 更新选择的字段

如果您只想在更新时更新或忽略某些字段，可以使用Select, Omit

db.Model(&user).Select("name").Updates(map[string]interface{}{"name": "hello", "age": 18, "actived": false})
//// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE id=111;
db.Model(&user).Omit("name").Updates(map[string]interface{}{"name": "hello", "age": 18, "actived": false})
//// UPDATE users SET age=18, actived=false, updated_at='2013-11-17 21:34:10' WHERE id=111;

4.4. 更新更改字段但不进行Callbacks

以上更新操作将执行模型的BeforeUpdate, AfterUpdate方法，更新其UpdatedAt时间戳，在更新时保存它的Associations，如果不想调用它们，可以使用UpdateColumn, UpdateColumns

// 更新单个属性，类似于`Update`
db.Model(&user).UpdateColumn("name", "hello")
//// UPDATE users SET name='hello' WHERE id = 111;
// 更新多个属性，与“更新”类似
db.Model(&user).UpdateColumns(User{Name: "hello", Age: 18})
//// UPDATE users SET name='hello', age=18 WHERE id = 111;

4.5. Batch Updates 批量更新

Callbacks在批量更新时不会运行

db.Table("users").Where("id IN (?)", []int{10, 11}).Updates(map[string]interface{}{"name": "hello", "age": 18})
//// UPDATE users SET name='hello', age=18 WHERE id IN (10, 11);
// 使用struct更新仅适用于非零值，或使用map[string]interface{}
db.Model(User{}).Updates(User{Name: "hello", Age: 18})
//// UPDATE users SET name='hello', age=18;
// 使用`RowsAffected`获取更新记录计数
db.Model(User{}).Updates(User{Name: "hello", Age: 18}).RowsAffected

4.6. 使用SQL表达式更新

DB.Model(&product).Update("price", gorm.Expr("price * ? + ?", 2, 100))
//// UPDATE "products" SET "price" = price * '2' + '100', "updated_at" = '2013-11-17 21:34:10' WHERE "id" = '2';
DB.Model(&product).Updates(map[string]interface{}{"price": gorm.Expr("price * ? + ?", 2, 100)})
//// UPDATE "products" SET "price" = price * '2' + '100', "updated_at" = '2013-11-17 21:34:10' WHERE "id" = '2';
DB.Model(&product).UpdateColumn("quantity", gorm.Expr("quantity - ?", 1))
//// UPDATE "products" SET "quantity" = quantity - 1 WHERE "id" = '2';
DB.Model(&product).Where("quantity > 1").UpdateColumn("quantity", gorm.Expr("quantity - ?", 1))
//// UPDATE "products" SET "quantity" = quantity - 1 WHERE "id" = '2' AND quantity > 1;

4.7. 在Callbacks中更改更新值

如果要使用BeforeUpdate, BeforeSave更改回调中的更新值，可以使用scope.SetColumn，例如

func (user *User) BeforeSave(scope *gorm.Scope) (err error) {
  if pw, err := bcrypt.GenerateFromPassword(user.Password, 0); err == nil {
    scope.SetColumn("EncryptedPassword", pw)
  }
}

4.8. 额外更新选项

// 为Update语句添加额外的SQL选项
db.Model(&amp;user).Set("gorm:update_option", "OPTION (OPTIMIZE FOR UNKNOWN)").Update("name, "hello")
//// UPDATE users SET name='hello', updated_at = '2013-11-17 21:34:10' WHERE id=111 OPTION (OPTIMIZE FOR UNKNOWN);

5. 删除/软删除

警告删除记录时，需要确保其主要字段具有值，GORM将使用主键删除记录，如果主要字段为空，GORM将删除模型的所有记录

// 删除存在的记录
db.Delete(&email)
//// DELETE from emails where id=10;
// 为Delete语句添加额外的SQL选项
db.Set("gorm:delete_option", "OPTION (OPTIMIZE FOR UNKNOWN)").Delete(&email)
//// DELETE from emails where id=10 OPTION (OPTIMIZE FOR UNKNOWN);

5.1. 批量删除

删除所有匹配记录

db.Where("email LIKE ?", "%jinzhu%").Delete(Email{})
//// DELETE from emails where email LIKE "%jinhu%";
db.Delete(Email{}, "email LIKE ?", "%jinzhu%")
//// DELETE from emails where email LIKE "%jinhu%";

5.2. 软删除

如果模型有DeletedAt字段，它将自动获得软删除功能！那么在调用Delete时不会从数据库中永久删除，而是只将字段DeletedAt的值设置为当前时间。

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;
// 软删除的记录将在查询时被忽略
db.Where("age = 20").Find(&user)
//// SELECT * FROM users WHERE age = 20 AND deleted_at IS NULL;
// 使用Unscoped查找软删除的记录
db.Unscoped().Where("age = 20").Find(&users)
//// SELECT * FROM users WHERE age = 20;
// 使用Unscoped永久删除记录
db.Unscoped().Delete(&order)
//// DELETE FROM orders WHERE id=10;

6. 关联

默认情况下，当创建/更新记录时，GORM将保存其关联，如果关联具有主键，GORM将调用Update来保存它，否则将被创建。

user := User{
    Name:            "jinzhu",
    BillingAddress:  Address{Address1: "Billing Address - Address 1"},
    ShippingAddress: Address{Address1: "Shipping Address - Address 1"},
    Emails:          []Email{
                                        {Email: "jinzhu@example.com"},
                                        {Email: "jinzhu-2@example@example.com"},
                   },
    Languages:       []Language{
                     {Name: "ZH"},
                     {Name: "EN"},
                   },
}
db.Create(&user)
//// BEGIN TRANSACTION;
//// INSERT INTO "addresses" (address1) VALUES ("Billing Address - Address 1");
//// INSERT INTO "addresses" (address1) VALUES ("Shipping Address - Address 1");
//// INSERT INTO "users" (name,billing_address_id,shipping_address_id) VALUES ("jinzhu", 1, 2);
//// INSERT INTO "emails" (user_id,email) VALUES (111, "jinzhu@example.com");
//// INSERT INTO "emails" (user_id,email) VALUES (111, "jinzhu-2@example.com");
//// INSERT INTO "languages" ("name") VALUES ('ZH');
//// INSERT INTO user_languages ("user_id","language_id") VALUES (111, 1);
//// INSERT INTO "languages" ("name") VALUES ('EN');
//// INSERT INTO user_languages ("user_id","language_id") VALUES (111, 2);
//// COMMIT;
db.Save(&user)

6.1. 创建/更新时跳过保存关联

默认情况下保存记录时，GORM也会保存它的关联，你可以通过设置gorm:save_associations为false跳过它。

db.Set("gorm:save_associations", false).Create(&user)
db.Set("gorm:save_associations", false).Save(&user)

6.2. tag设置跳过保存关联

您可以使用tag来配置您的struct，以便在创建/更新时不会保存关联

type User struct {
  gorm.Model
  Name      string
  CompanyID uint
  Company   Company `gorm:"save_associations:false"`
}
type Company struct {
  gorm.Model
  Name string
}

以上就是golang gorm的预加载及软删硬删的数据操作示例的详细内容，更多关于golang gorm数据预加载软删硬删的资料请关注软件开发网其它相关文章！

gorm 示例数据操作数据预加载 golang

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