var mysql=require('mysql');
var client=mysql.createClient({
    user:'mysql',
    password:''
});
client.useDatabase('test');
module.exports.get_chapter_list = function(subject_id){

    client.query("select distinct chapter_id from course_associations where subject_id="+subject_id+" and status_id=1",
            function(err,results,fields){
                    return results;
    });
  return "hello";
};

rs=require('./getChapterList');

rs.get_chapter_list(1);

// Output: hello

var mysql=require('mysql');
var client=mysql.createClient({
  user:'mysql',
  password:''
});
client.useDatabase('test');
module.exports.get_chapter_list = function(subject_id, callback){
  client.query("select distinct chapter_id from course_associations where subject_id="+subject_id+" and status_id=1",
        function(err,results,fields){
                callback( results );
});
return "hello";
};

var rs = require('./getChapterList');

rs.get_chapter_list(1, function(results) {
  console.log(results);
}
});

module.exports.get_chapter_list = function(subject_id, callback){
  client.query("select distinct chapter_id from course_associations where subject_id="+subject_id+" and status_id=1",
    function(err,results,fields){
      // doesn't contain any error handling
      callback(results);
  });
};

rs.get_chapter_list(1, function(results) {
   console.log(results); // or whatever you need to do with the results
});

exports.get_chapter_list = function(subject_id, callback) {
    client.query("select ...", callback);
};

...

var rs = require('./getChapterList');

rs.get_chapter_list(1, function(err, results) {
    if (err) {
        // handle error
    } else {
        // do something with results
        console.log(results);
    }
});