42.Scopes的使用(將當前數據庫連接傳遞到func(*DB) *DB
,可以用於動態添加條件)
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")
}
db.Scopes(AmountGreaterThan1000, PaidWithCreditCard).Find(&orders)
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(OrderStatus([]string{"paid", "shipped"})).Find(&orders)
43.指定表名
var deleted_users []User
db.Table("deleted_users").Find(&deleted_users)
44.更新全部字段
user.Name = "jinzhu 2"
user.Age = 100
db.Save(&user)
45.更新更改字段
// 更新單個屬性(如果更改)
db.Model(&user).Update("name", "hello")
// 使用`map`更新多個屬性,只會更新這些更改的字段
db.Model(&user).Updates(map[string]interface{}{"name": "hello", "age": 18, "actived": false})
// 使用`struct`更新多個屬性,只會更新這些更改的和非空白字段
db.Model(&user).Updates(User{Name: "hello", Age: 18})
46.批量更新
db.Table("users").Where("id IN (?)", []int{10, 11}).Updates(map[string]interface{}{"name": "hello", "age": 18})
db.Model(User{}).Updates(User{Name: "hello", Age: 18})
47. 使用SQL表達式更新
DB.Model(&product).Update("price", gorm.Expr("price * ? + ?", 2, 100))
48.刪除記錄
// 刪除存在的記錄
db.Delete(&email)
49.批量刪除
db.Where("email LIKE ?", "%jinzhu%").Delete(Email{})
50.軟刪除(如果模型有DeletedAt
字段,調用Delete
時不會從數據庫中永久刪除,而是隻將字段DeletedAt
的值設置爲當前時間)
//只會更新DeleteAt字段
db.Delete(&user)
db.Where("age = ?", 20).Delete(&User{})
//軟刪除的記錄查詢時會被忽略
db.Where("age = 20").Find(&user)
//使用Unscoped,在記錄查詢時帶上軟刪除的記錄
db.Unscoped().Where("age = 20").Find(&users)
//使用Unscoped永久刪除記錄
db.Unscoped().Delete(&order)
51.關聯(類似於Hibernate的級聯)
user := User{
Name: "jinzhu",
BillingAddress: Address{Address1: "Billing Address - Address 1"},
ShippingAddress: Address{Address1: "Shipping Address - Address 1"},
Emails: []Email{
{Email: "[email protected]"},
{Email: "jinzhu-2@[email protected]"},
},
Languages: []Language{
{Name: "ZH"},
{Name: "EN"},
},
}
db.Create(&user)
52.指定struct關聯
type User struct {
gorm.Model
Name string
CompanyID uint
Company Company `gorm:"save_associations:false"`
}
53.錯誤處理
if db.Model(&user).Related(&credit_card).RecordNotFound() {
// 沒有信用卡被發現處理...
}
54.事務
func CreateAnimals(db *gorm.DB) err {
tx := db.Begin()
// 注意,一旦你在一個事務中,使用tx作爲數據庫句柄
if err := tx.Create(&Animal{Name: "Giraffe"}).Error; err != nil {
tx.Rollback()
return err
}
tx.Commit()
return nil
}
55.執行原生SQL
db.Exec("DROP TABLE users;")
db.Exec("UPDATE orders SET shipped_at=? WHERE id IN (?)", time.Now, []int64{11,22,33})
56.sql.Rows
rows, err := db.Model(&User{}).Where("name = ?", "jinzhu").Select("name, age, email").Rows() // (*sql.Rows, error)
/*
rows, err := db.Raw("select name, age, email from users where name = ?", "jinzhu").Rows() // (*sql.Rows, error)
*/
defer rows.Close()
for rows.Next() {
...
rows.Scan(&name, &age, &email)
...
}
57.數據庫連接池
db.DB().SetMaxIdleConns(10)
db.DB().SetMaxOpenConns(100)