golang gorm的预加载及软删硬删的数据操作示例

目录

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

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