CODEWITHSUNDEEP
node.js
Asad ullah
Asad ullah

Reputation: 716

how to wait for first query results and then execute another query in node.js

I'm making an app in angular & node.js. At a certain point of code I need to execute INSERT query and then get back insertId and then make another INSERT into another table along with above insertId. But i'm always getting 0 as insertId because it does not wait for first query to be executed due to its async nature. So I need a work around to wait for first query results and then execute second query. My code looks like below.

insert_users_query = `INSERT INTO users xxxxxx`;
connection.query(insert_users_query, (err, result)=>{
    var user_id = result.insertId;
});

second_query = `INSERT INTO another_table (user_id) VALUES('${user_id}')`;
connection.query(linked_accounts_query, (err, result)=>{
// this query saves 0  as user_id in table.
});

I think this can be done via promises. But as I'm beginner in this stuff and read an article on Promises too but I can't figure out a simple solution. Any help will be highly appreciated!

Thanks.

Upvotes: 0

Views: 1453

Answers (2)

Helping hand
Helping hand

Reputation: 2930

You can use async/await for this as well instead of calling 2nd query inside 1st as it creates mess when number of queries increases.

But since connection.query returns a callback we need to wrap it inside a promise. 

async function main(){ 
  try{
    const insert_users_query = `INSERT INTO users xxxxxx`;
    const result = await queryDb(insert_users_query);
    let user_id = result.insertId;
    const linked_accounts_query = `INSERT INTO another_table (user_id) VALUES('${user_id}')`;
    await queryDb(linked_accounts_query);
  }
  catch(e){
    //catch error
  }
}

You can call this generic queryDb function returning promise for all the queries.

function queryDb(query){
  return new Promise( ( resolve, reject ) => {
      connection.query(query, (err, result)=>{
          if (err){
              return reject( err );
          }
          resolve( result );
      });
  })
}

Upvotes: 1

Rajan Lagah
Rajan Lagah

Reputation: 2528

You can do same by.

insert_users_query = `INSERT INTO users xxxxxx`;
connection.query(insert_users_query, (err, result)=>{// query 1( getting insertId as result.insertId)
    if(err){
     //handle error
    }else{
    var user_id = result.insertId; // using insertId
    second_query = `INSERT INTO another_table (user_id) VALUES('${user_id}')`;
    connection.query(linked_accounts_query, (err, result2)=>{//query2
  // this query saves 0  as user_id in table.
   }
 });



});

This is done by using callback you can use await for the same. This is bit simpler basically we will get err,result as object after the execution of query1 and then we can run another query using err,result of query1 in query1.

Upvotes: 1

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