Gorm使用详解
1.什么是Gorm
go语言编写的orm框架
特点：
1)全功能ORM
2)关联（包含一个，包含多个，属于，多对多）
3)Callbacks（创建/保存/更新/删除/查找前后回调）
4)预加载
5)事务
6)复合主键
7)SQL Builder（执行原生sql）
8)自动迁移
9)日志
2.安装
go get -u github.com/jinzhu/gorm
3.数据库连接
1)引入相应驱动
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)连接示例
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.自动迁移
创建表，缺少的列和索引，不会改变现有列的类型或删除列
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{})会创建/更新"users"表。
5.表结构操作
1)检验表是否存在
var result bool
result = db.HasTable(&User{})
fmt.Println(result)
运行结果：
true
2)创建表
db.CreateTable(&User{})
3)删除表
// 删除模型User对应的表
db.DropTable(&User{})
// 删除users表
db.DropTable("users")
4)修改列
db.Model(&User{}).ModifyColumn("description", "text")
5)删除列
db.model(&User{}).DropColumn("description")
6)添加外键
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)删除索引
db.Model(&User{}).RemoveIndex("idx_user_name")
6.模型Model定义
1)gorm.Model结构体
type Model struct {
ID uint `gorm:"primary_key"`
CreatedAt time.Time
UpdatedAt time.Time
DeletedAt *time.Time `sql:"index"`
}
2)定义Model结构体
// 默认表名是 Model名称的小写+复数
type Profile struct {
gorm.Model
Refer int
Name string
}
type User struct {
gorm.Model
Name string `gorm:"size:255"` //string默认长度255,size重设长度
Age int `gorm:"column:my_age"` //设置列名为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设置sql类型，unique_index为该列设置唯一索引`
Address string `gorm:"not null;unique"` //非空
no string `gorm:"index:idx_no"` // 创建索引并命名，如果有其他同名索引，则创建组合索引
code string `gorm:"index:idx_no"
`
Profile Profile `gorm:"ForeignKey:ProfileID;AssociationForeignKey:Refer"` //设置外键
ProfileID int
remark string `gorm:"default:'test'"` //默认值
}
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()
// 全局禁用表名复数
db.SingularTable(true)
db.AutoMigrate(&User{}, &Profile{})
}
3)自定义表名
// 自定义表名(方法一)
func (User) TableName() string{
return "my_user"
}
...
// 自定义表名(方法二)
db.Table("my_user").CreateTable(&User{})
8.创建
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`
9.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;
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)Where查询条件（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;
// 主键的Slice
db.Where([]int64{20, 21, 22}).Find(&users)
//// SELECT * FROM users WHERE id IN (20, 21, 22);
3)Not条件
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)带内联条件的查询
// 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;
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)
6)查询链
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
获取第一个匹配的记录，若没有，则根据条件初始化一个新的记录
// 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
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}
9)Assign
将参数分配给结果，不管是否找到
// 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
获取第一个匹配的结果，或创建一个具有给定条件的新纪录
// 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
从数据库检索字段
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
从数据库检索记录时指定顺序
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)
14)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)
15)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;
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)
18)Pluck
查询单列，返回数组
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)
19)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)
20)预加载
数据库编译一次，然后保存，提高执行效率
db.Preload("Orders").Find(&users)
10.更新
1)更新全部字段 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})
3)更新选择字段
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;
11.删除
1)删除
// 删除存在的记录
db.Delete(&email)
//// DELETE from emails where id=10;
2)批量删除
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)软删除
如果模型有DeletedAt字段，删除时是软删除
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;
12.事务
func CreateAnimals(db *gorm.DB) err {
tx := db.Begin()
// 注意，一旦你在一个事务中，使用tx作为数据库句柄
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构建
1)执行原生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.日志
// 启用Logger，显示详细日志
db.LogMode(true)
// 禁用日志记录器，不显示任何日志
db.LogMode(false)
// 调试单个操作，显示此操作的详细日志
db.Debug().Where("name = ?", "jinzhu").First(&User{})
15.架构
Gorm使用可链接的API, *gorm.DB是链的桥梁
db, err := gorm.Open("postgres", "user=gorm dbname=gorm sslmode=disable")
// 创建新关系
db = db.Where("name = ?", "jinzhu")
// 过滤更多
if SomeCondition {
db = db.Where("age = ?", 20)
} else {
db = db.Where("age = ?", 30)
}
if YetAnotherCondition {
db = db.Where("active = ?", 1)
}
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