My goal is to retrieve data from a MySQL database by calling methods to insert and read information. The reason I am doing this is because node.js operates asynchronously. Here is my code:
exports.list = function(req, res){
var moduleRows;
req.getConnection(function(err,connection){
var query = connection.query('SELECT * FROM questions WHERE module_id = ?',[X],function(err,rows)
{
for(var i = 0;i < rows.length;i++){
moduleRows = rows[i];
GetResults(moduleRows);
}
});
var GetResults = function(moduleRows) {
var RightAnswer = 0;
var WrongAnswer1 = 0;
var query = connection.query("SELECT * FROM studentsanswers WHERE Question = '"+moduleRows.question+"' ",function(err,rows2)
{
for(var ii = 0;ii < rows2.length;ii++){
if (rows2[ii].Answer == moduleRows.RightAnswer){
RightAnswer++;
}
else if (rows2[ii].Answer == moduleRows.WrongAnswer1){
WrongAnswer1++;
}
}
var Data = {
question: moduleRows.question,
RightAnswer: moduleRows.RightAnswer,
WrongAnswer1: moduleRows.WrongAnswer1,
NumberOfRightAnswer: RightAnswer,
NumberOfWrongAnswer1 : WrongAnswer1
};
insertResults(Data);
return;
});
}
var insertResults = function(Data) {
var query = connection.query("INSERT INTO statistics set ? ",Data, function(err, rows)
{
PrintResults();
return;
});
}
var PrintResults = function() {
var query = connection.query("SELECT * FROM statistics" ,function(err,rows)
{
res.render('StatisticsByModules',{page_title:"Questions - Node.js",data:rows});
return;
});
}
});
};
I'm encountering the following errors: Error: Can't set headers after they are sent. TypeError: req.next is not a function