Iterating through mysql table to fill array in Node

Question

I have a table swipe that I need to iterate through to fill an array that I can use to display a matches list to the user. The structure is the following (a valid match between two users):

Here is my raw logic to iterate through the table and get match objects that I will push into an array:

user = current_user_id;

for (swipes in swipe)
{
  if (id_user === user)
  {
    to_match === id_user_matched;
    for (swipes in swipe)
    {
        if (id_user === to_match && id_user_matched === user)
        {
            matches_list[].push({“id_match”: id_match, “id_user_matched”: to_match});
        }
    }
  }
}

How can I do this in my backend with either an sql query or Node code?

Thank you!

If I have understood well, you can create the mysql query in order to retrieve just to rows concerning to id_user you want. After that you can populate the array with the query result. — Wolfetto
– Wolfetto, Commented Jun 25, 2019 at 13:38

Joel Coehoorn · Accepted Answer · 2019-06-25 13:49:44Z

1

I know nothing about node, but the SQL you want to run will look something like this:

select s2.id_match, s1.id_user_matched
from swipe s1
inner join swipe s2 ON s2.id_user = s1.id_user_matched and s2.id_user_matched = @user
where s1.id_user = @user

answered Jun 25, 2019 at 13:49

Joel Coehoorn

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5 Comments

Joel Coehoorn Over a year ago

It work by joining the table to itself. This replaces the loops in the sample code from the question... run the query, and the results go directly into the matches_list array. But again, I've never used node, so figuring out how to run the query is up to you.

Martin Over a year ago

Amazing! What do s1 and s2 mean?

Joel Coehoorn Over a year ago

Table aliases, so you can distinguish the two instances of the table from each other.

Martin Over a year ago

Thank you Joel! It works like a charm, SQL seems to be very powerful, is my query realistic in a production environment?

Joel Coehoorn Over a year ago

Yes, this is realistic

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