Using $in and $lt to find data with specific array values in MongoDB

Question

I have a people collection with a timeline array containing a year when something happened to this person. For example the year they were born, like this:

db.people.insert({
  "timeline": [
    { "born_year": 1999 },
    { "other_event": 2005 }
  ]
});

I can query this collection for someone born 1999:

db.people.find({
  "timeline": { $in: [ { "born_year": 1999 } ] }
});

However, when using $lt to query for people born before 2000 I don't get any results at all:

db.people.find({
  "timeline": { $in: [ { "born_year": { $lt: 2000 } } ] }
});

Can anyone explain to me what I'm doing wrong here?

JohnnyHK · Accepted Answer · 2013-09-19 21:22:41Z

2

You should be using dot notation to target specific element properties rather than matching entire elements as objects:

db.people.find({
  "timeline.born_year": { $lt: 2000 }
});

This will find all docs that have a timeline array element with a property of born_year with a value < 2000.

For the exact comparison:

db.people.find({
  "timeline.born_year": 1999
});

edited Sep 19, 2013 at 21:22

answered Sep 19, 2013 at 21:15

JohnnyHK

313k70 gold badges632 silver badges479 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Brandon Over a year ago

This would require a minor structure change to the objects, but it would be a wise change.

pdahlberg Over a year ago

Btw, Brandon what kind of structure change would be wise to use and why? I'm just starting to learn MongoDB so all tips are welcome :)

Collectives™ on Stack Overflow

Using $in and $lt to find data with specific array values in MongoDB

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related