Proper RESTful API practice to run 2 queries in a function?

So I'm developing an API for mySQL with nodejs. Trying to make a function that inserts into two different tables.

INSERT INTO account_details (username, first_name, last_name, gender, mobile_number, postal_code, email, activated) VALUES (?, ?, ?, ?, ?, ?, ?, ?)

and

INSERT INTO passwords (username, password) VALUES (?, ?)

What's the proper way to do it?

Right now I have this, which works perfectly except it crashes my nodejs server, giving the error below.

    addUser(request, respond) {
        var userObject = new User(request.body.username, request.body.password, request.body.first_name, request.body.last_name, request.body.gender, request.body.mobile_number, request.body.postal_code, request.body.email, request.body.activated, null, null);
        var sql = "INSERT INTO account_details (username, first_name, last_name, gender, mobile_number, postal_code, email, activated) " +
                    "VALUES (?, ?, ?, ?, ?, ?, ?, ?)";
        var password = "INSERT INTO passwords (username, password) VALUES (?, ?)";

        var values = [userObject.getUsername(), userObject.getFirstName(), userObject.getLastName(), userObject.getGender(),
                    userObject.getMobileNumber(), userObject.getPostalCode(), userObject.getEmail(), userObject.getActivated()];
                
        var passvalues = [userObject.getUsername(), userObject.getPassword()];

        db.query(sql, values, function (error, result) {
            if (error) {
                throw error;
            }
            else {
                respond.json(result);
            }
        });
        db.query(password, passvalues, function (error, result) {
            if (error) {
                throw error;
            }
            else {
                respond.json(result);
            }
        });
    }

Error: Can't set headers after they are sent.

Can anyone help with the proper syntax? Thanks in advance.

You could change your code as below:

addUser(request, respond) {
    var userObject = new User(request.body.username, request.body.password, request.body.first_name, request.body.last_name, request.body.gender, request.body.mobile_number, request.body.postal_code, request.body.email, request.body.activated, null, null);
    var sql = "INSERT INTO account_details (username, first_name, last_name, gender, mobile_number, postal_code, email, activated) " +
                "VALUES (?, ?, ?, ?, ?, ?, ?, ?)";
    var password = "INSERT INTO passwords (username, password) VALUES (?, ?)";

    var values = [userObject.getUsername(), userObject.getFirstName(), userObject.getLastName(), userObject.getGender(),
                userObject.getMobileNumber(), userObject.getPostalCode(), userObject.getEmail(), userObject.getActivated()];

    var passvalues = [userObject.getUsername(), userObject.getPassword()];

    db.query(sql, values, function (error, result) {
        if (error) {
            throw error;
        }
        else {
            db.query(password, passvalues, function (error, result) {
              if (error) {
                throw error;
              }
              else {
                respond.json(result);
              }
            });
        }
    });
    
}

Because you're doing it twice

respond.json(result);

first one will succeed and the second one will throw the above error.

what you want to do is to wait for both of them to succeed and return result.

Consider using Promises and await both of those and then proceed to response.