Regarding nested Promises in NodeJS - node.js

Question

There are many threads on this and using that i am trying to find solution for below problem.
getMethod() {
execDBQuery(sqlQuery1)
.then(productionQueryRows => {
prodResultFunc(resultSet) // Calling a function to get another set of DB values
.then (result) {
console.log(result) // Final result which will be sent to user
}
});
}
async function prodResultFunc(prodRowSet) {
const results = await Promise.all(
prodRowSet.map( async (objBatchRow) => {
execDBQuery(sqlQuery2)
.then(resultSet => {
read value-1
})
execDBQuery(sqlQuery3)
.then(resultSet => {
read value-2
})
// Create a object using Value-1 & Value-2 and return object to map
});
);
}
I tried implementing below (with one just SQL execution) and it works fine.
async function prodResultFunc(prodRowSet) {
const results = await Promise.all(
prodRowSet.map( async (objBatchRow) => {
execDBQuery(sqlQuery2)
.then(resultSet => {
read values using resultSet
Create object with resultSet values
})
return object
});
);
}
But i want use values for both SQLs (2 & 3) for creating object and this where i am struggling to find syntax for implementation. Any help/pointers to existing threads will be a great help.

Answer 1

Whenever you're dealing with complex Promise chains, I find that the async/await syntax is much easier to read. You end up with a lot less nested code.
The example below shows how you might combine the results of two different queries:
const prodRowSet = [1,2,3];
// Mock query function.
async function execDBQuery(sql) {
return [{ id: 1, query: sql }];
}
async function prodResultFunc(prodRowSet) {
const results = await Promise.all(
prodRowSet.map( async (objBatchRow) => {
let resultSet2 = await execDBQuery('sqlQuery2');
let resultSet3 = await execDBQuery('sqlQuery3');
// Do whatever you want to combine the result sets.
let combinedObj = { resultSet2, resultSet3}
return combinedObj;
})
);
return results;
}
(async() => {
let output = await prodResultFunc(prodRowSet);
console.log("Output:", output);
})();

Answer 2

You might be looking for Promise.All
async function prodResultFunc(prodRowSet) {
const results = await Promise.all(
prodRowSet.map( async (objBatchRow) => {
Promise.all([execDBQuery(sqlQuery2), execDBQuery(sqlQuery3)]).then(function(values) {
//TODO:: Impement you business logic here
console.log(values);
});
});
);
}