只要看看你如何处理每个查询都会给予你一个can error或者一个结果，就像javascript处理error一样，你在回调中的第一个参数总是会给你一个can error，第二个是结果。所以你可以使用if else条件来处理它。

connection.query("INSERT INTO admin (nom, prenom, email, tel_fixe, adresse, nsiret, nom_entreprise, demande, code, tel_mob) VALUES ('" + nom + "','" + prenom + "','" + email + "','" + tel_fixe + "','" + adresse + "','" + siret + "','" + societe + "','" + demande + "','" + code + "','" + tel_mob + "')", function(err, rows) {
            if (err) {
console.log("===============err====================",err) // error is in this line
}
else{
                connection.query("SELECT * FROM admin WHERE  id='" + rows.insertId + "' LIMIT 1", function(err, rows) {
                    if (!err && rows.length > 0) {
                        res.json(rows[0]);
                    } else {
                        res.json([]);
                    }
                });
            }
        });

虽然这个问题是旧的，我遇到了同样的问题，我觉得这是需要回答它。它为我工作时，我把参数的sql查询如下这是非常清楚和方括号是必要的，当添加到查询。缺少方括号给出的错误不是rows.affectedRows.Refer here .

router.post('/', function(req, res, next) {
    pool.getConnection(function(err, connection) {
        var postBody = req.body;
        var params = [[postBody.nom,postBody.prenom,postBody.societ, postBody.adresse,postBody.siret,postBody.email,postBody.tel_fixe,ostBody.tel_mob,"",2]];
        connection.query("INSERT INTO admin (nom, prenom, email, tel_fixe, adresse, nsiret, nom_entreprise, demande, code, tel_mob) VALUES ?", [params], function(err, rows) {
            if (rows.affectedRows > 0) {
                connection.query("SELECT * FROM admin WHERE  id='" + rows.insertId + "' LIMIT 1", function(err, rows) {
                    if (!err && rows.length > 0) {
                        res.json(rows[0]);
                    } else {
                        res.json([]);
                    }
                });
            }
        });
    });
});
module.exports = router;

app.get('/addstudent',(req,res)=>{
    // res.send(req.query);
    const {name,phone,email,gender} = req.query
    let qry = "select * from test where email=? and phoneno=?";
    mysql.query(qry,[email,phone],(err,results)=>{
        if(err)
        throw err
        else{
            if(results.length > 0){

            }else{
                let qry2 = "insert into test values(?,?,?,?)";
                mysql.query(qry2,[name,phone,email,gender],(err,results)=>{
                    if(results.affectedRows>0){
                        res.render("add",{mesg:true})
                    }
                })
            }
        }
    })
})

error : Cannot read properties of unde`enter code here`fined (reading 'affectedRows')