Nested Json from nested mysql queries in Nodejs/ExpressJs - mysql

Question

I m fetching data from mysql database in nodejs/expressjs and want to create nested json from it.
I want to create Json object like this :
[
{id : 1,countryName:'USA',population:10000,
cities : [
{id:1,cityName:'NY',countryId:1},{id:2,cityName:'Chicago',countryId:1}
]
},
{id : 2,countryName:'Canada',population:20000,
cities : [
{id:1,cityName:'Toronto',countryId:2},{id:2,cityName:'Ottawa',countryId:2}
]
}
]
here is my code in expressJs but it is giving me an empty array of JSON
app.get("/checkJson",function(req,res){
var country = {};
var outerobj = {};
var outerArray = [];
conn.query("select * from country",function(err,result){
for(var i = 0 ;i<result.length;i++){
var cityobj = {};
var city = [];
conn.query("select * from city where countryId ="+result[i].id,function(err,cityResult){
for(var j = 0;j<cityResult.length;j++){
cityobj = {cityName:cityResult[j].name,countryId:cityResult[j].countryId};
city.push(cityobj);
} //end city forloop
}) //end city Query
outerobj = {id:result[i].id,countryName:result[i].name,pop:result[i].population,cities:city};
outerArray.push(outerobj);
} //end country forloop
}) // end country query
console.log(outerArray);
})

Answer 1

MySQL returns flat objects. We want to nest joined objects.
Let's say we have courses table, each course belongs to a department and has various course sections. We would like to have a resulting courses array that has a department object property within it and have a list of course sections.
This is a good solution from kyleladd on github
https://github.com/ravendano014/node-mysql-nesting