Go操作数据库

go提供了一些标准库让我们和数据库交互， database/sql是golang的标准库之一，它提供了一系列接口方法，用于访问关系数据库。不同的数据库驱动，需要去实现各种方法

func main(){
	db,err := sql.Open("mysql", "root:123456@tcp(127.0.0.1:3306)/htadmin")
}

此时会报错，说mysql 驱动不存在。安装mysql驱动

go get github.com/go-sql-driver/mysql
---------------------------------
import(
"database/sql"
_ "github.com/go-sql-driver/mysql"  //需要引入这个包
)

获取到db对象，查询用db.Query(sql), DDL操作用db.Exec(sql)，用Scan方法把结果赋值给模型实例

模型结构（和表对应）
type User struct {
	ID int64 `db:"id"`
	UserId int64 `db:"user_id"`
}
func main(){
	s := new(User);
	db,err := sql.Open("mysql", "root:123456@tcp(127.0.0.1:3306)/htadmin")	
	rows,err := db.Query("select id,user_id from user_addresses") //返回的字段数要和scan接受的参数一致
    results,err:=db.Exec("UPDATE message SET salary=? where id=?",8900,3)//这是更新语句
	for rows.Next(){
		rows.Scan(&s.UserId, &s.ID) //把查询出来的字段赋值给模型实例
		fmt.Println(s)
	}
}

网上找的封装的db操作方法

import (
	"database/sql"
	"fmt"
	"search/config"
	"strings"
)

type DbRow map[string]interface{}

type Dblib struct {
	db *sql.DB
}

func NewDblib() (*Dblib, error) {
	db, err := sql.Open("mysql", config.USERNAME+":"+config.PASSWORD+"@tcp("+config.MYSQL_SERVER+")/"+config.DATABASE)
	if err != nil {
		return nil, err
	}
	err = db.Ping()
	if err != nil {
		return nil, err
	}
	p := new(Dblib)
	p.db = db
	return p, nil
}

func scanRow(rows *sql.Rows) (DbRow, error) {
	columns, _ := rows.Columns()
	vals := make([]interface{}, len(columns))
	valsPtr := make([]interface{}, len(columns))

	for i := range vals {
		valsPtr[i] = &vals[i]
	}
	err := rows.Scan(valsPtr...)
	if err != nil {
		return nil ,err
	}

	r := make(DbRow)
	for i, v := range columns {
		if va, ok := vals[i].([]byte); ok {
			r[v] = string(va)
		} else {
			r[v] = vals[i]
		}
	}
	return r, nil
}

// 获取一行记录
func (d *Dblib) GetOne(sql string, args ...interface{}) (DbRow, error) {
	rows, err := d.db.Query(sql, args...)
	if err != nil {
		return nil, err
	}

	defer rows.Close()
	rows.Next()
	result, err := scanRow(rows)
	return result, err
}

// 获取多行记录
func (d *Dblib) GetAll(sql string, args ...interface{}) ([]DbRow, error) {
	rows, err := d.db.Query(sql, args...)
	if err != nil {
		return nil, err
	}

	defer rows.Close()

	result := make([]DbRow, 0)

	for rows.Next() {
		r, err := scanRow(rows)
		if err != nil {
			continue
		}

		result = append(result, r)
	}

	return result, nil

}
// 写入记录
func (d *Dblib) Insert(table string, data DbRow) (int64, error) {
	fields := make([]string, 0)
	vals := make([]interface{}, 0)
	placeHolder := make([]string, 0)

	for f, v := range data {
		fields = append(fields, f)
		vals = append(vals, v)
		placeHolder = append(placeHolder, "?")
	}

	sql := fmt.Sprintf("INSERT INTO %s(%s) VALUES(%s) ", table, strings.Join(fields, ","), strings.Join(placeHolder, ","))
	result, err := d.db.Exec(sql, vals...)
	if err != nil {
		return 0, err
	}

	lID, err := result.LastInsertId()
	if err != nil {
		return 0, err
	}

	return lID, nil
}

// 更新记录
func (d *Dblib) Update(table, condition string, data DbRow, args ...interface{}) (int64, error) {
	params := make([]string, 0)
	vals := make([]interface{}, 0)

	for f, v := range data {
		params = append(params, f + "=?")
		vals = append(vals, v)
	}

	sql := "UPDATE %s SET %s"
	if condition != "" {
		sql += " WHERE %s"
		sql = fmt.Sprintf(sql, table, strings.Join(params, ","), condition)
		vals = append(vals, args...)
	} else {
		sql = fmt.Sprintf(sql, table, strings.Join(params, ","))
	}

	result, err := d.db.Exec(sql, vals...)
	if err != nil {
		return 0, err
	}

	aID, err := result.RowsAffected()
	if err != nil {
		return 0, err
	}

	return aID, nil
}

// 删除记录
func (d *Dblib) Delete(table, condition string, args ...interface{}) (int64, error) {
	sql := "DELETE FROM %s "
	if condition != "" {
		sql += "WHERE %s"
		sql = fmt.Sprintf(sql, table, condition)
	} else {
		sql = fmt.Sprintf(sql, table)
	}

	result, err := d.db.Exec(sql, args...)
	if err != nil {
		return 0, err
	}

	aID, err := result.RowsAffected()
	if err != nil {
		return 0, err
	}

	return aID, nil

}

GO还有一些第三方库，方便我们和数据库交互，比如：

gorm操作数据库

http://gorm.book.jasperxu.com/crud.html#c 中文文档链接

1.安装第三方库

go get -u github.com/jinzhu/gorm

//创建User模型
type User struct{
	gorm.Model
    Name string `gorm:"column:name"` //gorm:"column:name"指定表的字段
	Email string `gorm:"column:email"`
	Password string `gorm:"column:password"`
}
func (u User) TableName() string{
	return "users" //这就是User模型绑定的表名，如果不指定，默认是模型复数
}
func main(){
	db,err := gorm.Open("mysql","root:123456@tcp(127.0.0.1:3306)/htadmin")
	defer db.Close()
	user:=User{ //创建一个模型对象并且实例化
		Name:     "张三",
		Email:    "[email protected]",
		Password: "$10$wqvwRQiHYOBCrR6dUdEzY.eYxC8XI9I6BUWPM8K.DzMEsjw66bX2K",
	}
	res := db.NewRecord(user)//检测主键是否存在,返回true
	db.Create(&user) //执行插入操作
    
    //查询操作，获取结果集one
    var one []User
	db.Table("users").Select("id,name,email,password").Where("name=?", "张三").Scan(&one)
	for _,v := range one{
		fmt.Println(v.ID,v.Name)
	}
}

常用查询方式

查询一条
var one User //如果查询一条数据，一个模型对象存储即可
db.First(&one,5) //where id=5
db.Where("name=?", "张三").First(&one) //where name="张三"

查询所有匹配结果集
var ones []User //数组
db.Where("name=?", "张三").Find(&ones)

//多个条件链式查询
db.Where("role = ?", "admin").Or("role = ?", "super_admin").Not("name = ?", "jinzhu").Find(&ones) 

//指定字段
db.Select("name, age").Find(&users) 
for _,v := range ones{
	fmt.Println(v.ID,v.Name)
}

gorm操作数据库

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