Sequelize - How to execute queries in sequence?

Question

I'm using sequelize 3.24.3 to connect to a MySQL database.

My requirement is to: execute query 1 and then execute query 2 after query 1 completes. Below is the code sample

Student.findOne({
    where:{
        userID:request.query.userID
    }
}).then(function(data){
    Papers.findAll({
            where:{
                userID:request.query.userID
            }
        }
    )
}).then(function (papers) {
    response.json({success: true,  paper: papers,});
}).catch(function (err) {
    console.log(err);
});

When the above runs: after findOne completes it calls the second "then" block and afterwards executes the findAll query. How can I prevent this and have it the queries executed sequentially?

Answer 1

Since you are using Sequelize you are also using bluebird.

You can use .all collection method, provided by the library. Read more about it in the documentation.

const Promise = require("bluebird");

Promise.all([
    Student.findOne({ where : { userID: request.query.userID } }),
    Papers.findAll({ where : { userID: request.query.userID } })
]).spread( function( student, papers ) {
    response.json({success: true,  paper: papers });
}).catch( function( error ) { 
    console.log(err);
});

This will execute Student.findOne and Papers.findAll together and after they both return results it will call the spread method with the two results.