I’ll introduce the condition for checking if elements exist in array fields in MongoDB.

The key point is the condition ‘arrayFieldName.0’ : { $exists: true }.

db.users.find({'friends.0': {$exists: true}})

When I write this occasionally, I think “Hmm? How do I write this again?”

Reference Information

• mongodb - Query for documents where array size is greater than 1 - Stack Overflow

That’s all from the Gemba.