go与xorm
参考
https://github.com/go-xorm/xorm/blob/master/README_CN.md
介绍
ORM，全称 Object Relational Mapping，中文叫作对象关系映射，通过它我们可以直接使用面向对象的方式做数据库开发，而不再直接写原生的SQL语句(甚至不需要SQL的基础)。通过把表映射成类，把行作为实例，把字段作为属性，ORM在执行对象操作的时候会把对应的操作转换为数据库原生语句的方式来完成数据库开发工作。
优点
1、优雅。使用这种ORM数据库抽象封装方式做开发，可以有效减少出现重复SQL语句的概率，写出来的模型也更直观清晰。
2、开发效率。ORM转换成底层数据库操作指令确实会有一些开销。只要不是对性能有严苛的要求，综合考虑开发效率的提升，代码重复利用率等因素，带来的好处要远大于性能损耗，而且项目越大其作越明显。
3、设计灵活。可以很轻松地写复杂的查询。
4、可移植。可以支持多个关系数据库引擎，近乎无痛地更换数据库。
使用数据库
连接
//需要引入_ "github.com/go-sql-driver/mysql"
engine, err := xorm.NewEngine("mysql", "root:123456@tcp(127.0.0.1:3306)/xorm_test?charset=utf8&parseTime=True&loc=Local")
创建表
type User struct {
Id int64
Name string
Salt string
Age int
Passwd string `xorm:"varchar(200)"`
Created time.Time `xorm:"created"`
Updated time.Time `xorm:"updated"`
}
err = engine.Sync2(new(User)) //将此struct同步到数据库
//相当于
//CREATE TABLE `user` (
//`id` bigint(20) NOT NULL AUTO_INCREMENT,
//`name` varchar(255) DEFAULT NULL,
//`salt` varchar(255) DEFAULT NULL,
//`age` int(11) DEFAULT NULL,
//`passwd` varchar(200) DEFAULT NULL,
//`created` datetime DEFAULT NULL,
//`updated` datetime DEFAULT NULL,
//PRIMARY KEY (`id`)
//) ENGINE=InnoDB DEFAULT CHARSET=utf8;插入
affected, err := engine.Insert(&user) //返回数据库中改变的条数
// INSERT INTO struct () values ()
affected, err := engine.Insert(&user1, &user2)
// INSERT INTO struct1 () values ()
// INSERT INTO struct2 () values ()
affected, err := engine.Insert(&users)
// INSERT INTO struct () values (),(),()
affected, err := engine.Insert(&user1, &users)
// INSERT INTO struct1 () values ()
// INSERT INTO struct2 () values (),(),()
user := User{1,"jim","",20,"qwer",time.Now(),time.Now()}
affected, err := engine.Insert(&user)单条查询
user := User{}
has, err := engine.Get(&user) //has表示查询对象是否存在
// SELECT * FROM user LIMIT 1
fmt.Println(has, user) //true {1 jim 20 qwer 2019-07-11 22:27:57 +0800 CST 2019-07-11 22:27:57 +0800 CST}
user = User{}
has, err = engine.Where("name = ?", "jim").Desc("id").Get(&user)
// SELECT * FROM user WHERE name = ? ORDER BY id DESC LIMIT 1
fmt.Println(user) //{1 jim 20 qwer 2019-07-11 22:27:57 +0800 CST 2019-07-11 22:27:57 +0800 CST}
var name string
has, err = engine.Table(&user).Where("id = ?", 1).Cols("name").Get(&name)
// SELECT name FROM user WHERE id = ?
fmt.Println(name) //jim
var id int64
has, err = engine.Table(&user).Where("name = ?", "jim").Cols("id").Get(&id)
fmt.Println(id) //1
has, err = engine.SQL("select id from user where name = ?","jim").Get(&id)
// SELECT id FROM user WHERE name = ?
fmt.Println(id) //1
var valuesMap = make(map[string]string)
has, err = engine.Table(&user).Where("id = ?", 1).Get(&valuesMap)
// SELECT * FROM user WHERE id = ?
fmt.Println(valuesMap) //map[age:20 created:2019-07-11T22:27:57+08:00 id:1 name:jim passwd:qwer salt: updated:2019-07-11T22:27:57+08:00]
var cols = []string{"id", "name", "age"}
var valuesSlice = make([]interface{}, len(cols))
has, err = engine.Table(&user).Where("id = ?", 1).Cols(cols...).Get(&valuesSlice)
// SELECT col1, col2, col3 FROM user WHERE id = ?
fmt.Println(valuesSlice) //[1 [106 105 109] 20]检查是否存在
has, err := engine.Exist(new(User))
// SELECT * FROM user LIMIT 1
has, err = engine.Exist(&User{
Name: "test1",
})
// SELECT * FROM user WHERE name = ? LIMIT 1
has, err = engine.Where("name = ?", "test1").Exist(&User{})
// SELECT * FROM user WHERE name = ? LIMIT 1
has, err = engine.SQL("select * from user where name = ?", "test1").Exist()
// select * from user where name = ?
has, err = engine.Table("user").Exist()
// SELECT * FROM user LIMIT 1
has, err = engine.Table("user").Where("name = ?", "test1").Exist()
// SELECT * FROM user WHERE name = ? LIMIT 1多条查询以及连表查询
var users []User
err = engine.Where("name = ?", "jim").And("age > 10").Limit(10, 0).Find(&users)
// SELECT * FROM user WHERE name = ? AND age > 10 limit 10 offset 0
fmt.Println(users) //[{1 jim 20 qwer 2019-07-11 22:27:57 +0800 CST 2019-07-11 22:27:57 +0800 CST}]
type Detail struct {
Id int64
UserId int64 `xorm:"index"`
}
type UserDetail struct {
User `xorm:"extends"`
Detail `xorm:"extends"`
}
detail := Detail{1,1}
detail2 := Detail{2,2}
detail3 := Detail{3,3}
affected, err := engine.Insert(&detail, &detail2, &detail3)
var users []UserDetail
err = engine.Table("user").Select("user.*, detail.*").
Join("INNER", "detail", "detail.user_id = user.id").
Where("user.name = ?", "jim").Limit(10, 0).Find(&users)
// SELECT user.*, detail.* FROM user INNER JOIN detail WHERE user.name = ? limit 10 offset 0
fmt.Println(users) //[{{1 jim 20 qwer 2019-07-11 22:27:57 +0800 CST 2019-07-11 22:27:57 +0800 CST} {1 1}}]根据条件遍历数据库
err = engine.Iterate(&User{}, func(idx int, bean interface{}) error {
user := bean.(*User)
fmt.Println(idx, user)
return nil
})
//0 &{1 jim 20 qwer 2019-07-11 22:27:57 +0800 CST 2019-07-11 22:27:57 +0800 CST}
//1 &{2 tom 20 qwer 2019-07-13 10:22:41 +0800 CST 2019-07-13 10:22:41 +0800 CST}
//2 &{3 jack 20 qwer 2019-07-13 10:22:41 +0800 CST 2019-07-13 10:22:41 +0800 CST}
// SELECT * FROM user
err := engine.BufferSize(100).Iterate(&User{Name:name}, func(idx int, bean interface{}) error {
user := bean.(*User)
return nil
})
// SELECT * FROM user Limit 0, 100
// SELECT * FROM user Limit 101, 100
rows, err := engine.Rows(&User{})
// SELECT * FROM user
defer rows.Close()
bean := new(User)
for rows.Next() {
err = rows.Scan(bean)
fmt.Println(bean)
}
//&{1 jim 20 qwer 2019-07-11 22:27:57 +0800 CST 2019-07-11 22:27:57 +0800 CST}
//&{2 tom 20 qwer 2019-07-13 10:22:41 +0800 CST 2019-07-13 10:22:41 +0800 CST}
//&{3 jack 20 qwer 2019-07-13 10:22:41 +0800 CST 2019-07-13 10:22:41 +0800 CST}更新数据，除非使用Cols,AllCols函数指明，默认只更新非空和非0的字段
user := User{Name:"jimmy"}
affected, err := engine.ID(1).Update(&user)
// UPDATE user SET ... Where id = 1
//变成{1 jimmy 20 qwer 2019-07-11 22:27:57 +0800 CST 2019-07-11 22:27:57 +0800 CST}
affected, err := engine.Update(&user, &User{Name:name})
// UPDATE user SET ... Where name = ?
var ids = []int64{1, 2, 3}
affected, err := engine.In(ids).Update(&user)
// UPDATE user SET ... Where id IN (?, ?, ?)
// force update indicated columns by Cols
affected, err := engine.ID(1).Cols("age").Update(&User{Name:name, Age: 12})
// UPDATE user SET age = ?, updated=? Where id = ?
// force NOT update indicated columns by Omit
affected, err := engine.ID(1).Omit("name").Update(&User{Name:name, Age: 12})
// UPDATE user SET age = ?, updated=? Where id = ?
affected, err := engine.ID(1).AllCols().Update(&user)
// UPDATE user SET name=?,age=?,salt=?,passwd=?,updated=? Where id = ?删除记录，需要注意，删除必须至少有一个条件，否则会报错。要清空数据库可以用EmptyTable
affected, err := engine.Where("id = ?",1).Delete(new(User))
// DELETE FROM user Where id = 1
fmt.Println(affected)
affected, err = engine.ID(2).Delete(new(User))
// DELETE FROM user Where id = 2获取记录总条数
counts, err := engine.Count(new(User))
// SELECT count(*) AS total FROM user求和函数
user := User{}
agesFloat64, err := engine.Sum(&user, "age")
// SELECT sum(age) AS total FROM user
fmt.Println(agesFloat64) //40
agesInt64, err := engine.SumInt(&user, "age")
// SELECT sum(age) AS total FROM user
fmt.Println(agesInt64) //40
sumFloat64Slice, err := engine.Sums(&user, "age", "id")
// SELECT sum(age), sum(id) FROM user
fmt.Println(sumFloat64Slice) //[40 7]
sumInt64Slice, err := engine.SumsInt(&user, "age", "id")
// SELECT sum(age), sum(id) FROM user
fmt.Println(sumInt64Slice) //[40 7]条件编辑器
err := engine.Where(builder.NotIn("a", 1, 2).And(builder.In("b", "c", "d", "e"))).Find(&users)
// SELECT id, name ... FROM user WHERE a NOT IN (?, ?) AND b IN (?, ?, ?)在一个Go程中多次操作数据库，但没有事务
session := engine.NewSession()
defer session.Close()
user1 := Userinfo{Username: "xiaoxiao", Departname: "dev", Alias: "lunny", Created: time.Now()}
if _, err := session.Insert(&user1); err != nil {
return err
}
user2 := Userinfo{Username: "yyy"}
if _, err := session.Where("id = ?", 2).Update(&user2); err != nil {
return err
}
if _, err := session.Exec("delete from userinfo where username = ?", user2.Username); err != nil {
return err
}
return nil在一个Go程中有事务
session := engine.NewSession()
defer session.Close()
// add Begin() before any action
if err := session.Begin(); err != nil {
// if returned then will rollback automatically
return err
}
user1 := Userinfo{Username: "xiaoxiao", Departname: "dev", Alias: "lunny", Created: time.Now()}
if _, err := session.Insert(&user1); err != nil {
return err
}
user2 := Userinfo{Username: "yyy"}
if _, err := session.Where("id = ?", 2).Update(&user2); err != nil {
return err
}
if _, err := session.Exec("delete from userinfo where username = ?", user2.Username); err != nil {
return err
}
// add Commit() after all actions
return session.Commit()事务的简写方法
res, err := engine.Transaction(func(session *xorm.Session) (interface{}, error) {
user1 := Userinfo{Username: "xiaoxiao", Departname: "dev", Alias: "lunny", Created: time.Now()}
if _, err := session.Insert(&user1); err != nil {
return nil, err
}
user2 := Userinfo{Username: "yyy"}
if _, err := session.Where("id = ?", 2).Update(&user2); err != nil {
return nil, err
}
if _, err := session.Exec("delete from userinfo where username = ?", user2.Username); err != nil {
return nil, err
}
return nil, nil
})上下文缓存，如果启用，那么针对单个对象的查询将会被缓存到系统中，可以被下一个查询使用。
sess := engine.NewSession()
defer sess.Close()
var context = xorm.NewMemoryContextCache()
var c2 ContextGetStruct
has, err := sess.ID(1).ContextCache(context).Get(&c2)
assert.NoError(t, err)
assert.True(t, has)
assert.EqualValues(t, 1, c2.Id)
assert.EqualValues(t, "1", c2.Name)
sql, args := sess.LastSQL()
assert.True(t, len(sql) > 0)
assert.True(t, len(args) > 0)
var c3 ContextGetStruct
has, err = sess.ID(1).ContextCache(context).Get(&c3)
assert.NoError(t, err)
assert.True(t, has)
assert.EqualValues(t, 1, c3.Id)
assert.EqualValues(t, "1", c3.Name)
sql, args = sess.LastSQL()
assert.True(t, len(sql) == 0)
assert.True(t, len(args) == 0)创建Engine组
dataSourceNameSlice := []string{masterDataSourceName, slave1DataSourceName, slave2DataSourceName}
engineGroup, err := xorm.NewEngineGroup(driverName, dataSourceNameSlice)masterEngine, err := xorm.NewEngine(driverName, masterDataSourceName)
slave1Engine, err := xorm.NewEngine(driverName, slave1DataSourceName)
slave2Engine, err := xorm.NewEngine(driverName, slave2DataSourceName)
engineGroup, err := xorm.NewEngineGroup(masterEngine, []*Engine{slave1Engine, slave2Engine})Query 最原始的也支持SQL语句查询，返回的结果类型为 []map[string][]byte。QueryString 返回 []map[string]string, QueryInterface 返回 []map[string]interface{}.
results, err := engine.Query("select * from user")
results, err := engine.Where("a = 1").Query()
results, err := engine.QueryString("select * from user")
results, err := engine.Where("a = 1").QueryString()
results, err := engine.QueryInterface("select * from user")
results, err := engine.Where("a = 1").QueryInterface()执行一个SQL语句
affected, err := engine.Exec("update user set age = ? where name = ?", age, name)