2、gorm

简介

全特性 ORM (几乎包含所有特性)
模型关联 (一对一，一对多，一对多（反向），多对多，多态关联)
钩子 (Before/After Create/Save/Update/Delete/Find)
预加载
事务
复合主键
SQL 构造器
自动迁移
日志
基于GORM回调编写可扩展插件
全特性测试覆盖
开发者友好

安装

go get -u github.com/jinzhu/gorm

模型定义

type Student struct {
    ObjId string `grom:"type:varcar(70);colmn:obj_id;primary_key"`
    Name  string
    age   int
}

模型结构体标签

标签	说明
Column	指定列的名称
Type	指定列的类型
Size	指定列的大小，默认是 255
PRIMARY_KEY	指定一个列作为主键
UNIQUE	指定一个唯一的列
DEFAULT	指定一个列的默认值
PRECISION	指定列的数据的精度
NOT NULL	指定列的数据不为空
AUTO_INCREMENT	指定一个列的数据是否自增
INDEX	创建带或不带名称的索引，同名创建复合索引
UNIQUE_INDEX	类似 `索引`，创建一个唯一的索引
EMBEDDED	将 struct 设置为 embedded
EMBEDDED_PREFIX	设置嵌入式结构的前缀名称
-	忽略这些字段

关联结构标签

标签	说明
MANY2MANY	指定连接表名称
FOREIGNKEY	指定外键
ASSOCIATION_FOREIGNKEY	指定关联外键
POLYMORPHIC	指定多态类型
POLYMORPHIC_VALUE	指定多态的值
JOINTABLE_FOREIGNKEY	指定连接表的外键
ASSOCIATION_JOINTABLE_FOREIGNKEY	指定连接表的关联外键
SAVE_ASSOCIATIONS	是否自动保存关联
ASSOCIATION_AUTOUPDATE	是否自动更新关联
ASSOCIATION_AUTOCREATE	是否自动创建关联
ASSOCIATION_SAVE_REFERENCE	是否引用自动保存的关联
PRELOAD	是否自动预加载关联

Model

gorm.Model 是一个包含一些基本字段的结构体, 包含的字段有 ID，CreatedAt， UpdatedAt， DeletedAt。

模型结构体如果有需要，可以内嵌gorm.Model结构体。

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

指定表名

表名默认是结构体名称的复数形式，可以使用db.SingularTable(true)关闭复数表名。

也可以自己指定表名，如下：

func (Student) TableName() string {
    return "school_stu"
}

连接数据库

首先导入数据库驱动程序，例如mysql

go get github.com/go-sql-driver/mysql

import _ "github.com/go-sql-driver/mysql"

gorm也包含了一部分的数据库驱动，所以也可以使用自带的

//MySQL
import _ "github.com/jinzhu/gorm/dialects/mysql"
//PostgreSQL
import _ "github.com/jinzhu/gorm/dialects/postgres"
//Sqlite3
import _ "github.com/jinzhu/gorm/dialects/sqlite"
//SQLServer
import _ "github.com/jinzhu/gorm/dialects/mssql

获取连接

MySql

注意：为了正确的处理 time.Time ，需要包含 parseTime 作为参数。

url := "root:123456@tcp(localhost:3306)/test?charset=utf8&parseTime=True&loc=Local"
db, err := gorm.Open("mysql", url)
defer db.Close()
if err != nil {
    fmt.Println(err)
    return
}

PostgreSQL

url := "host=localhost port=5432 user=postgres dbname=postgres password=123456 sslmode=disable TimeZone=Asia/Shanghai"
db, err := gorm.Open("postgres", url)
defer db.Close()
if err != nil {
    fmt.Println(err)
    return
}

Sqlite3

url := "/tmp/test.db"
db, err := gorm.Open("sqlite3", url)
defer db.Close()
if err != nil {
    fmt.Println(err)
    return
}

SQLServer

url := "sqlserver://user:passwd@localhost:1433?database=dbname"
db, err := gorm.Open("mssql", url)
defer db.Close()
if err != nil {
    fmt.Println(err)
    return
}

操作

插入

id, _ := uuid.NewRandom()
stu := Student{
    id.String(),
    "lucy",
    18,
}
db.Create(&stu)

注意：

所有包含零值的字段，像 0，''，false 或者其他的零值不会被保存到数据库中，但会使用这个字段的默认值。

钩子设置字段值

func (s *Student) BeforeCreate(scope *gorm.Scope) error {
	id, _ := uuid.NewRandom()
	scope.SetColumn("obj_id", id.String())
	return nil
}

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;

// 获取一条记录，不指定排序
db.Take(&user)
//// SELECT * FROM users 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;

// 获取所有的记录
db.Find(&users)
//// SELECT * FROM users;

// 通过主键进行查询 (仅适用于主键是数字类型)
db.First(&user, 10)
//// SELECT * FROM users WHERE id = 10;

// 通过主键进行查询 (仅适用于主键是数字类型)
db.First(&user, 23)
//// SELECT * FROM users WHERE id = 23 LIMIT 1;
// 非数字类型的主键查询
db.First(&user, "id = ?", "string_primary_key")
//// SELECT * FROM users WHERE id = 'string_primary_key' LIMIT 1;

// 原生 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;

Where

占位符形式

// 获取第一条匹配的记录
db.Where("name = ?", "jinzhu").First(&user)
//// SELECT * FROM users WHERE name = 'jinzhu' limit 1;

// 获取所有匹配的记录
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)

// BETWEEN
db.Where("created_at BETWEEN ? AND ?", lastWeek, today).Find(&users)

struct或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;

// 多主键 slice 查询
db.Where([]int64{20, 21, 22}).Find(&users)
//// SELECT * FROM users WHERE id IN (20, 21, 22);

Not

db.Not("name", "jinzhu").First(&user)
//// SELECT * FROM users WHERE name <> "jinzhu" LIMIT 1;

// 不包含
db.Not("name", []string{"jinzhu", "jinzhu 2"}).Find(&users)
//// SELECT * FROM users WHERE name NOT IN ("jinzhu", "jinzhu 2");

//不在主键 slice 中
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;

// 原生 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";

Or

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)
//// SELECT * FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2';

FirstOrInit

获取第一条匹配的记录，或者通过给定的条件下初始一条新的记录（仅适用与于 struct 和 map 条件）。

// 未查询到
db.FirstOrInit(&user, User{Name: "non_existing"})
//// user -> User{Name: "non_existing"}

// 查询到
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}

Attrs

如果未找到记录，则使用参数初始化 struct

// 未查询到
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}

// 查询到
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}

Assign

无论是否查询到数据，都将参数赋值给 struct

// 未查询到
db.Where(User{Name: "non_existing"}).Assign(User{Age: 20}).FirstOrInit(&user)
//// user -> User{Name: "non_existing", Age: 20}

// 查询到
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}

FirstOrCreate

获取第一条匹配的记录，或者通过给定的条件创建一条记录（仅适用与于 struct 和 map 条件）。

// 未查询到
db.FirstOrCreate(&user, User{Name: "non_existing"})
//// INSERT INTO "users" (name) VALUES ("non_existing");
//// user -> User{Id: 112, Name: "non_existing"}

// 查询到
db.Where(User{Name: "Jinzhu"}).FirstOrCreate(&user)
//// user -> User{Id: 111, Name: "Jinzhu"}

子查询

db.Where("amount > ?", DB.Table("orders").Select("AVG(amount)").Where("state = ?", "paid").QueryExpr()).Find(&orders)
// SELECT * FROM "orders"  WHERE "orders"."deleted_at" IS NULL AND (amount > (SELECT AVG(amount) FROM "orders"  WHERE (state = 'paid')));

Order

db.Order("age desc, name").Find(&users)
//// SELECT * FROM users ORDER BY age desc, name;

// 多个排序条件
db.Order("age desc").Order("name").Find(&users)
//// SELECT * FROM users ORDER BY age desc, name;

// 重新排序
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)

Limit

db.Limit(3).Find(&users)
//// SELECT * FROM users LIMIT 3;

// 用 -1 取消 LIMIT 限制条件
db.Limit(10).Find(&users1).Limit(-1).Find(&users2)
//// SELECT * FROM users LIMIT 10; (users1)
//// SELECT * FROM users; (users2)

Offset

db.Offset(3).Find(&users)
//// SELECT * FROM users OFFSET 3;

// 用 -1 取消 OFFSET 限制条件
db.Offset(10).Find(&users1).Offset(-1).Find(&users2)
//// SELECT * FROM users OFFSET 10; (users1)
//// SELECT * FROM users; (users2)

Count

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;

Group 和 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)

Joins

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)

// 多个关联查询
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)

Scan

将 Scan 查询结果放入另一个结构体中

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)

简介

安装