express数据库链接

链接mongodb方式：

1. 原始require('mongodb')包方式:
const MongoClient = require('mongodb').MongoClient;
const DB_CONN_STR = 'mongodb://localhost:27017/test';
let insertData = function(db, data, callback) {
    let collection = db.collection('person');
    collection.insert(data, function(err, result) {
        if (err) {
            console.log('Error:' + err);
            return;
        }
        callback(result);
    })
}
MongoClient.connect(DB_CONN_STR, function(err, db) {
    console.log('连接成功！');
    let data = [{ "name": "tom", "age": "99" }];
    insertData(db, data, function(result) {
        console.log(result);
        db.close();
    })
    selectData(db, function(result) {
        console.log(result);
        db.close();
    });
})
2. 使用mongoose中间件链接：

链接mysql的方式：

1.原始链接方式：
const mysql = require('mysql');
let connection = mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: '368532',
    database: 'world'
});
connection.connect();
connection.query('SELECT 1 + 1 AS solution', function(err, rows, fields) {
    if (err) throw err;
    console.log('The solution is: ', rows[0].solution);
});
connection.end();
2.mysql中pool方式: mysql.createPool({})
3.使用中间件express-myconnection链接：