MongoDB : querying documents with two equal fields, $match and $eq

Question

What is the best way to return all documents in a collection if I want document.a == document.b?

I\'ve tried

db.collection.aggregate([ { $match: { $         


        

Answer 1

If I understood your question right you want those documents that have same values in field1 and field2.

For this try

db.coll.find({$where: function() { return this.field1 == this.field2 } } );

or more compact

db.coll.find({ $where : "this.field1 == this.field2" } );