Best way to fetch data from many tables in node.js

Question

If I have a view in my (mvc project) contains data from many tables in the database, what is the best way to fetch them without getting into the nested tree of doom

Model1.findAll().then(model1Data => {
  Model2.findAll().then(model2Data => {
    Model3.findAll().then(model3Data => {
      Modeln.findAll().then(modelnData => {
        res.render('view', {
          model1Data: model1Data,
          model2Data: model2Data,
          model3Data: model3Data,
          modelnData: modelnData
        });
      })
    })
  })
})

Note: the above query has no where clauses, joins, or any other conditions

If you have Sequelize Associations beetwin your Models, you can use Include to extract all the data link If not, you can consider have a separated folder that contains all your models logic and call each required function, also, this should be helpful if you need show some info in other views (not all data) — masmerino
– masmerino, Commented Dec 19, 2018 at 14:29
Already I have a separated folder for the models logic, but the same problem will happens when I call each one because the returned value will be promise and I have to use nesting to can use them at all — Ebrahim Mansour
– Ebrahim Mansour, Commented Dec 19, 2018 at 14:43

Vivek Doshi · Accepted Answer · 2018-12-19 14:44:50Z

3

Here you can use 2 ways either Promise.all() or async/await :

Promise.all() :

const promises = [
    Model1.findAll(),
    Model2.findAll(),
    Model3.findAll(),
    Modeln.findAll()
]

Promise.all(promises).then((data) => {
    res.render('view', data );
});

Async/await :

let model1Data = await Model1.findAll();
let model2Data = await Model2.findAll();
let model3Data = await Model3.findAll();
let modelnData = await Modeln.findAll();
res.render('view', {
    model1Data: model1Data,
    model2Data: model2Data,
    model3Data: model3Data,
    modelnData: modelnData
});

NOTE :

I would suggest to use Promise.all() if the queries are not dependent on each other , as it will start execution and don't wait for the first one to complete as it does in async/await.

For More Deatil : DO READ

edited Dec 19, 2018 at 14:44

answered Dec 19, 2018 at 14:39

Vivek Doshi

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2 Comments

Ebrahim Mansour Over a year ago

The first way works well with my, but the second one gives me the following error: SyntaxError: await is only valid in async function

Vivek Doshi Over a year ago

Yes you have to put async before function your_func_name(), please. See any async await function you will get idea ,

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