javascript - 异步 Node js "For"循环与数据库查询

Question

这里是“for”循环，用于为数组中的每个“id”运行查询(SQLite3 数据库)。

qry = "SELECT patients.*, patient_visits.visit_id,patient_visits.patient_id, patient_visits.visitdate, patient_visits.visittime FROM patients LEFT JOIN patient_visits ON patients.id = patient_visits.patient_id "+where+" GROUP BY patients.id ORDER BY patients.id  DESC LIMIT "+limit+" OFFSET "+offset;
db.all(qry, (err, results) => {
    if(err){
        response.error = err;
        res.send(response);
    }else{
        response.patients = patients;
        for (var i = 0; i < patients.length; i++) {
            response.patients[i].check = "false";
            var patient = response.patients[i];
            db.each("SELECT visit_id FROM patient_visits where patient_id='"+patient.id+"' AND visitdate >='"+moment().format('YYYY-MM-DD')+"'", function(err, row) {
                if (row) {
                    response.patients[i].check = "true";
                }
            });
        }
    }
    res.send(response);
});

问题在于 for 循环在查询完成之前继续进行。有没有办法检查查询是否完成？

Answer 1

请导入异步模块。

qry = "SELECT patients.*, patient_visits.visit_id,patient_visits.patient_id, patient_visits.visitdate, patient_visits.visittime FROM patients LEFT JOIN patient_visits ON patients.id = patient_visits.patient_id " + where + " GROUP BY patients.id ORDER BY patients.id  DESC LIMIT " + limit + " OFFSET " + offset;
db.all(qry, (err, results) => {
    if (err) {
        response.error = err;
        res.send(response);
    } else {
        response.patients = patients;

        async.forEachOf(patients, function (patient, key, callback) {
            db.each("SELECT visit_id FROM patient_visits where patient_id='" + patients[key] + "' AND visitdate >='" + moment().format('YYYY-MM-DD') + "'", function (err, row) {
                if (row) {
                    response.patients[i].check = "true";
                }else{
                    callback();
                }
            });
        }, function (error) {
            if (error) {
                console.log(error)
            } else {
                res.send(response);
            }
        })

    }
});