go 的 mysql 的简单操作

关于 sql：https://studygolang.com/articles/3022

异常处理： http://www.jianshu.com/p/f30da01eea97

一、数据库的连接及初始化

// demo_db.go

package main

import (
	"database/sql"
	"fmt"
	_ "github.com/go-sql-driver/mysql"
)

var (
	db *sql.DB
)

func check(err error) {
	if err != nil {
		fmt.Println(err)
	}
}

func InitDB(mydb *sql.DB) {
	db = mydb
}

func main() {
	mydb, err := sql.Open("mysql", "root:root@tcp(localhost:3306)/imooc")
	check(err)
	defer mydb.Close()

	InitDB(mydb)
	fmt.Println(db)
}

二、增删改查

// demo_method.go

package main

import (
	"database/sql"
	"fmt"
	_ "github.com/go-sql-driver/mysql"
)

var (
	db *sql.DB
)

func check(err error) {
	if err != nil {
		fmt.Println(err)
	}
}

func InitDB(mydb *sql.DB) {
	db = mydb
}

func DemoExec() {
	sql_insert := "insert user set username=?"
	result, err := db.Exec(sql_insert, "xiaoming")
	check(err)
	rows, err := result.RowsAffected()
	check(err)
	fmt.Printf("rows affected: %d\n", rows)
}

func DemoQuery() {
	sql_query := "select acctid from account where money=?"
	rows, err := db.Query(sql_query, 2000)
	defer rows.Close()
	check(err)
	for rows.Next() {
		var id int
		if err := rows.Scan(&id); err != nil {
			fmt.Println(err)
		}
		fmt.Printf("id: %d\n", id)
	}
}

func DemoQueryRow() {
	var id int
	sql_query := "select acctid from account where money=?"
	row := db.QueryRow(sql_query, 2000)
	err := row.Scan(&id)
	check(err)
	fmt.Printf("id: %d\n", id)
}

func DemoPrepare() {
	stmt, err := db.Prepare("select username from user where userid=?")
	check(err)

	rows, err := stmt.Query(3)
	defer rows.Close()
	check(err)

	for rows.Next() {
		var username string
		if err := rows.Scan(&username); err != nil {
			fmt.Println(err)
		}
		fmt.Printf("username: %s\n", username)
	}
}

func main() {
	mydb, err := sql.Open("mysql", "root:root@tcp(localhost:3306)/imooc")
	check(err)
	defer mydb.Close()
	InitDB(mydb)

	DemoExec()
	DemoQuery()
	DemoQueryRow()
	DemoPrepare()
}

三、事务

// demo_transaction.go

package main
import (
    "database/sql"
    _ "github.com/go-sql-driver/mysql"
    "fmt"
    "log"
)

var (
    db *sql.DB
    tx *sql.Tx
)

func check(err error) {
    if err != nil {
        fmt.Println(err)
    }
}

func InitDB(mydb *sql.DB) {
    db = mydb
}

func InitTx(mytx *sql.Tx) {
    tx = mytx
}

func CheckAccountAvaiable(acctid int) {
    sql := "select * from account where acctid=?"
    rows,err := tx.Query(sql, acctid)
    // 如果不调用rows.Close，conn无法回到 tx上
    defer rows.Close()
    if err != nil {
        log.Println(err)
        panic(fmt.Sprintf("查询错误，账号%d不可得!", acctid))
    }
    if !rows.Next() {
        panic(fmt.Sprintf("查询失败，账号%d不可得!", acctid))
    }
}

func HasEnoughMoney(acctid, money int) {
    sql := "select * from account where acctid=? and money>=?"
    rows,err := tx.Query(sql, acctid, money)
    defer rows.Close()
    if err != nil {
        log.Println(err)
        panic(fmt.Sprintf("用户%d余额查询失败！", acctid))
    }
    if !rows.Next() {
        panic(fmt.Sprintf("用户%d余额不足！", acctid))
    }
}

func ReduceMoney(acctid, money int) {
    sql := "update account set money = money-? where acctid = ?"
    _,err := tx.Exec(sql, money, acctid)
    if err != nil {
        log.Println(err)
        panic(fmt.Sprintf("用户%d减款失败！", acctid))
    }
}

func AddMoney(acctid, money int) {
    sql := "update account set money =money+? where acctid = ?"
    _,err := tx.Exec(sql, money, acctid)
    if err != nil {
        log.Println(err)
        panic(fmt.Sprintf("用户%d加款失败！", acctid))
    }
}

func Transfer(source_acctid, target_acctid, money int) {
    tx,err :=  db.Begin()
    check(err)
    InitTx(tx)

    defer func() {
        if err := recover(); err != sql.ErrTxDone && err != nil {
            fmt.Printf("出错了 ERR:%s\n", err)
            tx.Rollback()
        } else {
            tx.Commit()
            fmt.Printf("%d转给%d一共%d元, 转账成功！",source_acctid, target_acctid, money)
        }
    }()

    CheckAccountAvaiable(source_acctid)
    CheckAccountAvaiable(target_acctid)
    HasEnoughMoney(source_acctid, money)
    ReduceMoney(source_acctid, money)
    AddMoney(target_acctid, money)
}

func main() {
    mydb,err := sql.Open("mysql", "root:root@tcp(localhost:3306)/imooc")
    check(err)
    defer mydb.Close()

    InitDB(mydb)
    Transfer(4, 3, 500)
}

sql 脚本

$ source imooc.sql

imooc.sql

-- MySQL dump 10.16  Distrib 10.1.28-MariaDB, for Linux (x86_64)
--
-- Host: localhost    Database: imooc
-- ------------------------------------------------------
-- Server version    10.1.28-MariaDB

/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;
/*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */;
/*!40103 SET TIME_ZONE='+00:00' */;
/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;

--
-- Table structure for table `account`
--

DROP TABLE IF EXISTS `account`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `account` (
  `acctid` int(11) NOT NULL AUTO_INCREMENT,
  `money` int(6) DEFAULT NULL,
  PRIMARY KEY (`acctid`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `account`
--

LOCK TABLES `account` WRITE;
/*!40000 ALTER TABLE `account` DISABLE KEYS */;
INSERT INTO `account` VALUES (1,2000),(2,1300),(3,2800),(4,4000);
/*!40000 ALTER TABLE `account` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `user`
--

DROP TABLE IF EXISTS `user`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `user` (
  `userid` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(11) DEFAULT NULL,
  PRIMARY KEY (`userid`)
) ENGINE=InnoDB AUTO_INCREMENT=18 DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `user`
--

LOCK TABLES `user` WRITE;
/*!40000 ALTER TABLE `user` DISABLE KEYS */;
INSERT INTO `user` VALUES (1,'lisi'),(2,'zhangsan'),(3,'liuqi'),(4,'white'),(5,'xiaoming'),(6,'xiaoming'),(7,'xiaoming'),(8,'xiaoming'),(9,'xiaoming'),(10,'xiaoming'),(11,'xiaoming'),(12,'xiaoming'),(13,'xiaoming'),(14,'xiaoming'),(15,'xiaoming'),(16,'xiaoming'),(17,'xiaoming');
/*!40000 ALTER TABLE `user` ENABLE KEYS */;
UNLOCK TABLES;
/*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

-- Dump completed on 2017-10-15 20:27:53