How to compare fields in Meteor find query

Question

In a meteor find query how can I compare two fields? I want to do something like the following SQL query.

select * from games g where g.game_minutes > (minutes_since_midnight_now - g.game_duration)

In view of the answers below I did some experimenting along the way to comparing two fields:

this works:

      var nextGame = Games.findOne(
              {
               game_minutes: {$gt: minutesSinceMidnight},
               court_id: court,
               game_date: {$gt: yesterday}
              },
              {
               sort: {game_minutes: 1}
              }
              );

this does not work:

      var nextGame = Games.findOne(
              {
               $where: "this.game_minutes" > minutesSinceMidnight, 
               court_id: court,
               game_date: {$gt: yesterday}
              },
              {
               sort: {game_minutes: 1}
              }
              );

Ultimately I want something like this:

$where: "this.game_minutes" > (minutesSinceMidnight - "this.game_duration"),

score 2 · Answer 1 · edited May 23 '17 at 11:44

2

games.find({game_minutes: {$gt: minutes_since_midnight_now - g.game_duration}});

As seen here: How to use $min mongo query in Meteor.js?

Update: To compare two attributes of a document you would have to use a games.find({$where: "this.game_minutes > minutes_since_midnight_now - this.game_duration"}) or similar.

edited May 23 '17 at 11:44

Community

1
1

answered Oct 25 '14 at 12:13

Ayonix

1,872
1
15
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g.game_duration is another field in the same document. – markhorrocks Oct 25 '14 at 12:16
Then you'll need something like this: http://stackoverflow.com/questions/8433046/mongodb-query-with-fields-in-the-same-documents – Ayonix Oct 25 '14 at 12:42
So, in my case would it be something like $where: "this.game_minutes > minutesSinceMidnight - this.game_duration"? – markhorrocks Oct 26 '14 at 01:10

score 2 · Answer 2 · answered Nov 01 '14 at 11:44

Since you haven't specified why the following doesn't work...

var nextGame = Games.findOne(
          {
           $where: "this.game_minutes" > minutesSinceMidnight, 
           court_id: court,
           game_date: {$gt: yesterday}
          },
          {
           sort: {game_minutes: 1}
          }
          );

...I'm going to guess it is because Mongodb expects either a string or a function to the $where clause. I'm also guessing you have tried what Ayonix suggested in his comment, to use...

$where: "this.games_minutes > minutes_since_midnight_now - this.game_duration"

...and that this did not work. Without trying it myself, I'm thinking Mongodb has no way of evaluating what "minutes_since_midnigt_now" is when executing and parsing the $where string you passed it.

However, $where also seems to accept a full javascript function, so maybe this will work instead:

var nextGame = Games.findOne(
          {
           $where: function () { return this.game_minutes > minutesSinceMidnight - this.game_duration; },

           court_id: court,
           game_date: {$gt: yesterday}
          },
          {
           sort: {game_minutes: 1}
          }
          );

If this doesn't work, maybe you can disclose some more details as of what is happening when it "doesn't work"? Do you see an error? Doesn't it compile? Or does it simply not return anything at all?

It simply did not return a result. No error. I will try your suggestion. Minutes_since_midnight is a variable I set. — markhorrocks, Nov 01 '14 at 12:35

How to compare fields in Meteor find query

2 Answers2