node.js 异步使用 SQL

Posted 2023-03-07

【中文标题】node.js 异步使用 SQL

【英文标题】：node.js async using SQL

【发布时间】：2021-07-29 04:13:09

【问题描述】：

我需要在执行其余代码（包括具有相同问题的其他查询）之前从查询中获取结果。现在我有一个建立 sql 连接的文件，如下所示：

const mysql = require("mysql");
const config = require("./configuration/config.json");

var conn = mysql.createConnection ( 
    host: config.host,
    user: config.user,
    password: config.password,
    database: config.database
);
module.exports = conn;

然后我获取信息以检索工作会话的 API 代码如下所示：

const bodyParser = require("body-parser");
const router = require("express").Router();
const conn = require("../mysqldb");

router.get("/", async (req, res) => 
  console.log(`GET class report called for: project = $req.query.project and week of $req.query.date`);
  var date = req.query.date;
  var proj = req.query.project;
  var theReport = [];
  //Might not need date info
  var weekStart = new Date(date);
  var weekInMilliseconds = 7 * 24 * 60 * 60 * 1000;
  var weekEnd = new Date();
  weekEnd.setTime(weekStart.getTime() + weekInMilliseconds);

  const getProjectReport = async (proj, start, end) => 
    console.log(`getProject called for project $proj within date $date & $weekEnd`);
    var uids = [];
    // Find the sessions given the date and the project code
    let sql = "select uid from user;"
    conn.query(sql, (err, rows) => 
      if (err) 
        return res.status(500).json( error: err );
      
      else 
        for (let l = 0; l < rows.length; l++) 
          uids.push(rows[l]);
        
      
    );
    let qry = "SELECT * FROM work_session WHERE date BETWEEN (DATE('" + date + "')) AND (DATE('" + date + "') + 6) AND project = '" + proj + "';"
    conn.query(qry, (err, rows) => 
      if (err) 
        return res.status(500).json( error: err );
      
      else 
        //for all users in DB
        for (let u = 0; u < uids.length; u++) 
          let timeWorked = 0.0;
          let sessions = [];
          //for all work sessions
          for (let w = 0; w < rows.length; w++) 
            if (uids[u].uid == rows[w].uid) 
              timeWorked = timeWorked + hoursWrked(rows[w].starthr, rows[w].startmin, rows[w].finishhr, rows[w].finishmin);
              sessions.push(rows[w]);
            
          
          //If there was time works (AKA if a user with data was found and info recorded)
          if (timeWorked > 0) 
            // Query for user information
            let qry = "select * from user where uid = " + uids[u].uid + ";"
            conn.query(qry, (err, rows) => 
              if (err) 
                return res.status(500).json( error: err );
              
              else 
                var jsonString =  email: rows[0].email, hours: timeWorked, lname: rows[0].lname, fname: rows[0].fname, sessiontimes: sessions, weekS: req.query.date, weekE: weekEnd ;
                theReport.push(jsonString);
              
            );
          
        
      
    );
    //return the report
    return theReport;
  

  function hoursWrked(startHr, startMin, finishHr, finishMin) 
    let hours = finishHr - startHr;
    let minutes = finishMin - startMin;
    if (hours < 0) 
      hours = hours + 24;
    
    if (minutes < 0) 
      minutes = minutes + 60;
      hours = hours - 1;
    
    let time = hours + minutes / 60;
    totalTime = Math.round(100 * time) / 100;

    return totalTime;
  

  var theReport = await getProjectReport(proj, weekStart, weekEnd);
  console.log(theReport);
  if (theReport[0]) 
    console.log("Got it");
    return res.status(200).send(theReport);
  
  else 
    console.log("darn");
    return res.status(400).send( msg: "No projects/users found." );
  
);
module.exports = router;

我相信如果它全部异步运行，这应该可以工作，问题是它没有，并且在查询完成运行之前它运行了一半。任何和所有的帮助将不胜感激！

【参考方案1】：

您的 await 调用仅在视为异步的函数范围内有效。两者都调用 getProjectReport 异步，然后

 var theReport = await getProjectReport(proj, weekStart, weekEnd);

不会按预期工作。

【讨论】：

那么如何解决这个问题？我尝试在 getProjectReport 异步函数的括号内移动该行，但仍然有问题