sql base nodejs py go操作基本的db

const mysql = require('mysql2');

const connection = mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: 'root',
    database: 'mybatis_plus'
});

// simple query
connection.query('SELECT * FROM `user`',
    function(err, results, fields) {
        console.log(results); // results contains rows returned by server
        // console.log(fields); // fields contains extra meta data about results, if available
    }
);

import pymysql.cursors

# Connect to the database
connection = pymysql.connect(host='localhost',
                             user='root',
                             password='root',
                             database='mybatis_plus',
                             cursorclass=pymysql.cursors.DictCursor)

with connection:
    with connection.cursor() as cursor:
        # Create a new record
        sql = "INSERT INTO `user` ( `name`,`age`,`email`) VALUES ( %s, %s, %s)"
        cursor.execute(sql, ('newPystudy', '150', 'webmaster@python.org'))

    # connection is not autocommit by default. So you must commit to save
    # your changes.
    connection.commit()

    with connection.cursor() as cursor:
        # Read a single record
        sql = "SELECT `uid`, `name`,`age`,`email` FROM `user`"
        cursor.execute(sql)
        # result = cursor.fetchone()
        result = cursor.fetchall()
        print(result)
        print(len(result))

package main

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

func main() {
  fmt.Println("begin ...")

  //for i := 0; i < 100; i++ {
  //  fmt.Println(i)
  //}

  //r := gin.Default()
  //
  //r.GET("/", func(c *gin.Context) {
  //  fmt.Println(c.Params)
  //
  //  c.JSON(http.StatusOK, gin.H{
  //    "code": 20000,
  //    "message": "success",
  //    "data": gin.H{},
  //  })
  //})
  //
  //r.Run(":8080")

  testDB()
}

type User struct {
  uid   int
  age   int
  name  string
  email string
}

func testDB() {
  err := initDB() // 调用输出化数据库的函数
  if err != nil {
    fmt.Printf("init db failed,err:%v\n", err)
    return
  }

  //queryRowDemo()
  queryMultiRowDemo()
}

// 查询单条数据示例
func queryRowDemo() {
  sqlStr := "select uid, name, age, email from user where uid=?"
  var u User
  // 非常重要：确保QueryRow之后调用Scan方法，否则持有的数据库链接不会被释放
  err := db.QueryRow(sqlStr, 1).Scan(&u.uid, &u.name, &u.age, &u.email)
  if err != nil {
    fmt.Printf("scan failed, err:%v\n", err)
    return
  }
  fmt.Printf("id:%d name:%s age:%d email:%s \n", u.uid, u.name, u.age, u.email)
}

// 查询多条数据示例
func queryMultiRowDemo() {
  sqlStr := "select uid, name, age, email from user"
  rows, err := db.Query(sqlStr)
  if err != nil {
    fmt.Printf("query failed, err:%v\n", err)
    return
  }
  // 非常重要：关闭rows释放持有的数据库链接
  defer rows.Close()

  var users []User

  // 循环读取结果集中的数据
  for rows.Next() {
    var u User
    err := rows.Scan(&u.uid, &u.name, &u.age, &u.email)
    if err != nil {
      fmt.Printf("scan failed, err:%v\n", err)
      return
    }
    fmt.Printf("id:%d name:%s age:%d email:%s \n", u.uid, u.name, u.age, u.email)
    users = append(users, u)
  }

  println("users -----------------------")
  println(len(users))

  for _, v := range users {
    println(v.uid, v.name, v.age, v.email)
  }

  //var arr []int
  //arr = append(arr, 1)
  //arr = append(arr, 2)
  //println(len(arr))
  //
  //for i, v := range arr {
  //  println(i, v)
  //}

}

var db *sql.DB

// 定义一个初始化数据库的函数
func initDB() (err error) {
  // DSN:Data Source Name
  dsn := "root:root@tcp(127.0.0.1:3306)/mybatis_plus?charset=utf8mb4&parseTime=True"
  // 不会校验账号密码是否正确
  // 注意！！！这里不要使用:=，我们是给全局变量赋值，然后在main函数中使用全局变量db
  db, err = sql.Open("mysql", dsn)
  if err != nil {
    return err
  }
  // 尝试与数据库建立连接（校验dsn是否正确）
  err = db.Ping()
  if err != nil {
    return err
  }
  return nil
}