mongodb join-like query with two collections and a where clause

Question

Suppose we have following collections in a database:

db.documents.insert([{\'name\': \'A\'}, {\'name\': \'B\'}, {\'name\': \'C\'}])
db.fragments.insert([{\'v         


        

Answer 1

db.fragments.find( { 'doc_name': { $in : ['A' , 'B'] } } ); 

Execute this commands in mongo:

var f = db.documents.find().limit(2) , n = [];
for (var i = 0; i < f.length(); i++) n.push(f[i]['name']);
db.fragments.find( { 'doc_name': { $in : n } } );