Question

我刚开始学习Node.js，因此我仍然习惯于异步编程，回调和Promise。我试图从一个记录集中的多个MSSQL查询返回数据，但是我发现的大多数帮助文章都是关于MySQL的。

我尝试按照此处接受的答案中显示的步骤操作：Synchronous database queries with Node.js

在我的SQL函数中，当我打印到控制台时，它正确显示了对象。当我将其退回我的快递路由器并尝试打印该值时，它表示未定义。

这是我的MSSQL函数：

var config = require('../../db/config');

async function getJobData(jobID) {

   const sql = require('mssql');
   let sqlResult = {};

   var lock = 2;

   var finishRequest = function() {
       // This prints the values properly
       console.log(sqlResult['jobData']['recordset']);
       console.log(sqlResult['jobText']['recordset']);

       return sqlResult;
   }

   // first query
   try {
        await sql.connect(config)
        let result = await sql.query(`SELECT * FROM Jobs WHERE JobID = ${jobID}`);

        lock -= 1;
        sqlResult['jobData'] = result;
        sql.close();
        if (lock === 0) {
            finishRequest();
        }
    } catch (err) {
        // ... error checks
        console.log(err);
    }

   // second query
   try {
        await sql.connect(config)
        let result = await sql.query(`SELECT * FROM JDSectionTxt WHERE JobID = ${jobID} ORDER BY TypeID, OrderID`);

        lock -= 1;
        sqlResult['jobText'] = result;
        sql.close();
        if (lock === 0) {
            finishRequest();
        }
    } catch (err) {
        // ... error checks
        console.log(err);
    }
}

module.exports = getJobData;

这是我的特快路由器：

const express = require('express');
//....
const app = express();
//....

// Job Descriptions - Edit
app.get('/jds/edit', (req, res) => {
    const getJobData = require("../models/jds/getJobData");

    let jobID = 0;

    if(req.query.jobID){
        jobID = parseInt(req.query.jobID);
    }

    let jobData = getJobData(jobID);

    jobData.then(result => {
        //This just prints 'undefined'
        console.log(result);

        res.render('jds/edit', {

            data: result
        });
    }).catch(err => {
        console.log(err);
    });

})

我需要在此处进行哪些更改以正确地从SQL查询中传递对象，以使结果不不确定？

Answer 1

我认为您正在使其复杂化。这是应该满足您需求的代码：

var config = require('../../db/config');
const sql = require('mssql');

async function getJobData(jobID) {
    let sqlResult = {};

    await sql.connect(config)

    let firstAwait = getFirstQuery(jobID);
    let secondAwait = getSecondQuery(jobID);

    sqlResult['jobData'] = await firstAwait;
    sqlResult['jobText'] = await secondAwait;

    return sqlResult;
}

async function getFirstQuery(jobID) {
    try {

        return await sql.query(`SELECT * FROM Jobs WHERE JobID = ${jobID}`);
    } catch (err) {
        // ... error checks
        console.log(err);
    }
}

async function getSecondQuery(jobID) {
    try {
        return await sql.query(`SELECT * FROM JDSectionTxt WHERE JobID = ${jobID} ORDER BY TypeID, OrderID`);
    } catch (err) {
        // ... error checks
        console.log(err);
    }
}

module.exports = getJobData;

Answer 2

我认为您错过了退货声明。在第一个和第二个查询try / catch块中，您都应输入return finishRequest()。

Answer 3

您尚未将结果返回给函数，因此它以未定义的形式发送它，您可以像这样更新语句，以查看代码中有什么更新，请查找注释//这是更新的语句

var config = require('../../db/config');
function getJobData(jobID) {
sql = require('mssql');
sqlResult = {};
lock = 2;
var finishRequest = function() {
   // This prints the values properly
   console.log(sqlResult['jobData']['recordset']);
   console.log(sqlResult['jobText']['recordset']);

   return sqlResult;
}
try {
await sql.connect(config)
let result = await sql.query(`SELECT * FROM Jobs WHERE JobID = ${jobID}`);

    lock -= 1;
    sqlResult['jobData'] = result;
    sql.close();
    if (lock === 0) {
        finishRequest();
    }
} catch (err) {
    // ... error checks
    console.log(err);
}
// second query
try {
    await sql.connect(config)
    let result = await sql.query(`SELECT * FROM JDSectionTxt WHERE JobID = ${jobID} ORDER BY TypeID, OrderID`);

    lock -= 1;
    sqlResult['jobText'] = result;
    sql.close();
    if (lock === 0) {
        finishRequest();
    }
} catch (err) {
    // ... error checks
    console.log(err);
}
// this is updated statement
return sqlResult;
}
module.exports = getJobData;

Answer 4

尽管我对async / await不太熟悉，但我相信波纹管代码应该可以工作。

var config = require('../../db/config');

async function getJobData(jobID) {

    const sql = require('mssql');
    let sqlResult = {};

    try {

        await sql.connect(config)
        sqlResult['jobData'] = await sql.query(`SELECT * FROM Jobs WHERE JobID = ${jobID}`);

    } catch (err) {}

    try {

        sqlResult['jobText'] = await sql.query(`SELECT * FROM JDSectionTxt WHERE JobID = ${jobID} ORDER BY TypeID, OrderID`);
        sql.close();

    } catch (err) {}

    return sqlResult;
}

module.exports = getJobData;

您不需要锁，因为当您使用 await 时，代码实际上是同步的。如果您使用回调，则将需要锁。

Node.js-从多个MSSQL查询返回数据

4 个答案: