Question

我正在尝试使用Node和Express创建一个api路由，我必须说我没有太多经验。知道我有以下代码：

app.get('/api/place/:id', (req, res) => {
var id = req.params.id;
var message_error = '{"status": "failed", "message": "Unable to fetch data"}';

db.query("SELECT `id`, `user`, `lat`, `lon`, `elevation`, `rating`, `rating_count`, `country`, `continent`, `locality` FROM `t_points` WHERE id = ?", [id], (err, res1) => {
    if(err) {
        res.json(message_error);
    } else {
        //Store the user id from the points table and use it to fetch user datas
        var userId = res1[0].user;
        if(userId != null) {
            db.query("SELECT `id`, `name` FROM `t_users` WHERE `id` = ?", [userId], (err, res2) => {
                if(err) {
                    res.json(message_error);
                } else {
                    //Final json structure
                    res.json({
                        id: res1[0].id,
                        lat: res1[0].lat,
                        lon: res1[0].lon,
                        elevation: res1[0].elevation,
                        rating: res1[0].rating,
                        rating_count: res1[0].rating_count,
                        user: {
                            id: res2[0].id,
                            name: res2[0].name
                        }
                    });
                }
            });
        } else {
            res.json({
                id: res1[0].id,
                lat: res1[0].lat,
                lon: res1[0].lon,
                elevation: res1[0].elevation,
                rating: res1[0].rating,
                rating_count: res1[0].rating_count
            });
         }
      }    
  });
});

我正在对JSON结构进行硬编码，因此，如果表中的userId为null，则不会在json中打印用户对象，否则会打印它。但这不是一个好主意，因为我还将在同一路径中添加更多查询。是否有一种简单的方法在所有查询的末尾仅创建一个json，并且如果某些值为null则不显示它？

此外，最好使用async和await函数来代替它吗？

谢谢！

Answer 1

在查询数据时使用 util 可能更好地获取结果。

const mysql = require('mysql');
const util = require('util');

// ? connection pool
let db = mysql.createPool({
    connectionLimit: 10,
    host: 'localhost',
    port: 3306,
    user: 'root',
    password: 'secretpass',
    database: 'yourdatabasename'
});

// ? check connection
db.getConnection((err, connection) => {
    if (err) {
        console.log('database connection failed');
    } else {
        console.log('database connection resolved');
        connection.release();
    }
});

// ? formatter query
function queryString(spName, ...queryParam) {
    return mysql.format(spName, queryParam);
}

// ? do query
let performQuery = util.promisify(db.query).bind(db)

module.exports = {
    performQuery,
    queryString
}

然后像这样使用上面的函数：

app.get('/api/place/:id', async (req, res) => {
    const id = req.params.id;
    const message_error = '{"status": "failed", "message": "Unable to fetch data"}';
    
    try {
      let prepareOne = queryString(SELECT `id`, `user`, `lat`, `lon`, `elevation`, `rating`, `rating_count`, `country`, `continent`, `locality` FROM `t_points` WHERE id = ?", id);
      let resultOne = await performQuery(prepareOne);
      let userId = resultOne[0].user;
      if (userId != null) {
          let prepareTwo = queryString("SELECT `id`, `name` FROM `t_users` WHERE `id` = ?", userId);
      let resultTwo = await performQuery(prepareTwo);
      res.json({
                 ...resultOne,
                 user: {
                         ...resultTwo
                        }
                 });
      }
    } catch (err) {
      res.send(message_error);
    }

一个最终的自定义JSON中的多个查询

1 个答案: