Gorm使用詳解

1.什麼是Gorm
go語言編寫的orm框架
特色：
1)全功能ORM
2)關聯（包含一個，包含多個，屬於，多對多）
3)Callbacks（建立/保存/更新/刪除/查找先後回調）
4)預加載
5)事務
6)複合主鍵
7)SQL Builder（執行原生sql）
8)自動遷移
9)日誌

2.安裝

go get -u github.com/jinzhu/gorm

3.數據庫鏈接
1)引入相應驅動

import _ "github.com/jinzhu/gorm/dialects/mysql"
// import _ "github.com/jinzhu/gorm/dialects/postgres"
// import _ "github.com/jinzhu/gorm/dialects/sqlite"
// import _ "github.com/jinzhu/gorm/dialects/mssql"

2)鏈接示例
Mysql

import (
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/mysql"
)

func main() {
  db, err := gorm.Open("mysql", "user:password@/dbname?charset=utf8&parseTime=True&loc=Local")
  defer db.Close()
}

PostgreSQL

import (
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/postgres"
)

func main() {
  db, err := gorm.Open("postgres", "host=myhost user=gorm dbname=gorm sslmode=disable password=mypassword")
  defer db.Close()
}

Sqlite3

import (
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/sqlite"
)

func main() {
  db, err := gorm.Open("sqlite3", "/tmp/gorm.db")
  defer db.Close()
}

4.自動遷移
建立表，缺乏的列和索引，不會改變現有列的類型或刪除列

package main

import (
    "fmt"
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/postgres"
    "time"
)

const (
    host = "127.0.0.1"
    port = 5432
    user = "postgres"
    password = "1"
    dbname = "dm-identity"
)

type User struct {
    gorm.Model
    Name string
    Age int
    Birthday time.Time
}

func main() {
    psqlInfo := fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s sslmode=disable", host, port, user, password, dbname)

    db, err := gorm.Open("postgres", psqlInfo)
    if err != nil{
        panic(err)
    }else{
        fmt.Println("connected successfully")
    }
    defer db.Close()

    db.AutoMigrate(&User{})
}

db.AutoMigrate(&User{})會建立/更新"users"表。

5.表結構操做
1)檢驗表是否存在

var result bool
result = db.HasTable(&User{})
fmt.Println(result)

運行結果：

true

2)建立表

db.CreateTable(&User{})

3)刪除表

// 刪除模型User對應的表
db.DropTable(&User{})

// 刪除users表
db.DropTable("users")

4)修改列

db.Model(&User{}).ModifyColumn("description", "text")

5)刪除列

db.model(&User{}).DropColumn("description")

6)添加外鍵

db.Model(&User{}).AddForeignKey("city_id","cities(id)")

7)添加索引

db.Model(&User{}).AddIndex("idx_user_name", "name")

db.Model(&User{]).AddUniqueIndex("idx_user_name", "name")

8)刪除索引

db.Model(&User{}).RemoveIndex("idx_user_name")

6.模型Model定義
1)gorm.Model結構體

type Model struct {
    ID        uint `gorm:"primary_key"`
    CreatedAt time.Time
    UpdatedAt time.Time
    DeletedAt *time.Time `sql:"index"`
}

2)定義Model結構體

// 默認表名是 Model名稱的小寫+複數
type Profile struct {
    gorm.Model
    Refer int
    Name  string
}

type User struct {
  gorm.Model
  Name string  `gorm:"size:255"` //string默認長度255,size重設長度
  Age int `gorm:"column:my_age"` //設置列名爲my_age
  Num int  `gorm:"AUTO_INCREMENT"` //自增
  IgnoreMe int `gorm:"-"` // 忽略字段
  Email string `gorm:"type:varchar(100);unique_index"//type設置sql類型，unique_index爲該列設置惟一索引`
  Address string `gorm:"not null;unique"` //非空
  no string `gorm:"index:idx_no"` // 建立索引並命名，若是有其餘同名索引，則建立組合索引
  code string `gorm:"index:idx_no"
  `
  Profile Profile `gorm:"ForeignKey:ProfileID;AssociationForeignKey:Refer"` //設置外鍵
  ProfileID int
  remark string `gorm:"default:'test'"` //默認值
}

func main() {
    psqlInfo := fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s sslmode=disable", host, port, user, password, dbname)

    db, err := gorm.Open("postgres", psqlInfo)
    if err != nil{
        panic(err)
    }
    defer db.Close()
    
    // 全局禁用表名複數
    db.SingularTable(true)
    
    db.AutoMigrate(&User{}, &Profile{})
}

3)自定義表名

// 自定義表名(方法一)
func (User) TableName() string{
    return "my_user"
}
...
// 自定義表名(方法二)
db.Table("my_user").CreateTable(&User{})

8.建立

user := User{Name: "Jinzhu", Age: 18, Birthday: time.Now()}

db.NewRecord(user) // => 主鍵爲空返回`true`

db.Create(&user)

db.NewRecord(user) // => 建立`user`後返回`false`

9.查詢

// 獲取第一條記錄，按主鍵排序
db.First(&user)
//// SELECT * FROM users ORDER BY id LIMIT 1;

// 獲取最後一條記錄，按主鍵排序
db.Last(&user)
//// SELECT * FROM users ORDER BY id DESC LIMIT 1;

// 獲取全部記錄
db.Find(&users)
//// SELECT * FROM users;

// 使用主鍵獲取記錄
db.First(&user, 10)
//// SELECT * FROM users WHERE id = 10;

1)Where查詢條件(簡單SQL)

// 獲取第一個匹配記錄
db.Where("name = ?", "jinzhu").First(&user)
//// SELECT * FROM users WHERE name = 'jinzhu' limit 1;

// 獲取全部匹配記錄
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)Where查詢條件（Struct & Map）

// 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;

// 主鍵的Slice
db.Where([]int64{20, 21, 22}).Find(&users)
//// SELECT * FROM users WHERE id IN (20, 21, 22);

3)Not條件

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";

4)帶內聯條件的查詢

// 按主鍵獲取
db.First(&user, 23)
//// SELECT * FROM users WHERE id = 23 LIMIT 1;

// 簡單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;

5)Or條件查詢

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)

6)查詢鏈

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)

7)FirstOrInit
獲取第一個匹配的記錄，若沒有，則根據條件初始化一個新的記錄

// 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}

8)Attrs
若是未找到記錄，則使用參數初始化結構

// 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}

9)Assign
將參數分配給結果，無論是否找到

// 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}

10)FirstOrCreate
獲取第一個匹配的結果，或建立一個具備給定條件的新紀錄

// 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"}

11)Select
從數據庫檢索字段

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;

12)Order
從數據庫檢索記錄時指定順序

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)

13)Limit
指定要檢索的記錄數

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)

14)Offset
指定在開始返回記錄以前要跳過的記錄數

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)

15)Count
獲取模型的記錄數

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;

16)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)

17)Join
指定鏈接條件

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)

// 多個鏈接與參數
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)

18)Pluck
查詢單列，返回數組

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)

// 要返回多個列，作這樣：
db.Select("name, age").Find(&users)

19)Scan
將結果掃描到另外一個結構中

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)

20)預加載
數據庫編譯一次，而後保存，提升執行效率

db.Preload("Orders").Find(&users)

10.更新
1)更新所有字段 Save

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;

2)更新更改字段 Update Updates

// 更新單個屬性（若是更改）
db.Model(&user).Update("name", "hello")
//// UPDATE users SET name='hello', updated_at='2013-11-17 21:34:10' WHERE id=111;

// 使用組合條件更新單個屬性
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})
//// 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})
//// UPDATE users SET name='hello', age=18, updated_at = '2013-11-17 21:34:10' WHERE id = 111;

// 警告:當使用struct更新時，FORM將僅更新具備非空值的字段
// 對於下面的更新，什麼都不會更新爲""，0，false是其類型的空白值
db.Model(&user).Updates(User{Name: "", Age: 0, Actived: false})

3)更新選擇字段

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)使用sql表達式更新

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;

11.刪除
1)刪除

// 刪除存在的記錄
db.Delete(&email)
//// DELETE from emails where id=10;

2)批量刪除

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%";

3)軟刪除
若是模型有DeletedAt字段，刪除時是軟刪除

db.Delete(&user)
//// UPDATE users SET deleted_at="2013-10-29 10:23" WHERE id = 111;

// 批量刪除
db.Where("age = ?", 20).Delete(&User{})
//// UPDATE users SET deleted_at="2013-10-29 10:23" WHERE age = 20;

// 軟刪除的記錄將在查詢時被忽略
db.Where("age = 20").Find(&user)
//// SELECT * FROM users WHERE age = 20 AND deleted_at IS NULL;

// 使用Unscoped查找軟刪除的記錄
db.Unscoped().Where("age = 20").Find(&users)
//// SELECT * FROM users WHERE age = 20;

// 使用Unscoped永久刪除記錄
db.Unscoped().Delete(&order)
//// DELETE FROM orders WHERE id=10;

12.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做爲數據庫句柄

  if err := tx.Create(&Animal{Name: "Giraffe"}).Error; err != nil {
     tx.Rollback()
     return err
  }

  if err := tx.Create(&Animal{Name: "Lion"}).Error; err != nil {
     tx.Rollback()
     return err
  }

  tx.Commit()
  return nil
}

13.SQL構建
1)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})

// Scan
type Result struct {
    Name string
    Age  int
}

var result Result
db.Raw("SELECT name, age FROM users WHERE name = ?", 3).Scan(&result)

2)sql.Row & sql.Rows

row := db.Table("users").Where("name = ?", "jinzhu").Select("name, age").Row() // (*sql.Row)
row.Scan(&name, &age)

rows, err := db.Model(&User{}).Where("name = ?", "jinzhu").Select("name, age, email").Rows() // (*sql.Rows, error)
defer rows.Close()
for rows.Next() {
    ...
    rows.Scan(&name, &age, &email)
    ...
}

// Raw SQL
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)
    ...
}

3)迭代中使用sql.Rows的Scan

rows, err := db.Model(&User{}).Where("name = ?", "jinzhu").Select("name, age, email").Rows() // (*sql.Rows, error)
defer rows.Close()

for rows.Next() {
  var user User
  db.ScanRows(rows, &user)
  // do something
}

14.日誌

// 啓用Logger，顯示詳細日誌
db.LogMode(true)

// 禁用日誌記錄器，不顯示任何日誌
db.LogMode(false)

// 調試單個操做，顯示此操做的詳細日誌
db.Debug().Where("name = ?", "jinzhu").First(&User{})

15.架構
Gorm使用可連接的API, *gorm.DB是鏈的橋樑

db, err := gorm.Open("postgres", "user=gorm dbname=gorm sslmode=disable")

// 建立新關係
db = db.Where("name = ?", "jinzhu")

// 過濾更多
if SomeCondition {
    db = db.Where("age = ?", 20)
} else {
    db = db.Where("age = ?", 30)
}
if YetAnotherCondition {
    db = db.Where("active = ?", 1)
}