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Can you fake a join in Mongo aggregation


According to the MongoDB Aggregation docs there's no direct equivalent for SQL's JOIN, which would allow aggregating data from multiple collections in a single query.


Categories : Mongodb

Related to : Can you fake a join in Mongo aggregation
Mongo aggregation with conditional date aggregation
A few problems in there so a bit beyond a comment. Mostly you were not enclosing several date operators with {} and as such producing invalid JSON inside an array. It helps if you change your indentation style as well to make it easier to spot formatting problems. I also personally prefer to stick to fully strict JSON notation, it parses well with other languages and is easier to "lint", which is

Categories : Mongodb
How to find match in documents in Mongo and Mongo aggregation?
What you are really asking here is how to make MongoDB return something that is actually quite different from the form in which you store it in your collection. The standard query operations do allow a "limitted" form of "projection", but even as the title on the page shared in that link suggests, this is really only about "limiting" the fields to display in results based on what is present in you

Categories : Mongodb
Mongo Aggregation
You can sort and then limit your request. $top_five_other = iterator_to_array($db->find(array('category'=>'other')->sort(array('published_date'=>-1))->limit(5));

Categories : Javascript
Mongo aggregation slow
If MongoDB has to load a large number of documents into memory (900,000 being a goodly amount) it is going to take some time. The way to improve this is... improve your hardware use sharding to distribute the load Sharding will work well if the group reduces the number of documents significantly. This is because the initial group work will be done on each shard and then re-done on the MongoS.

Categories : Mongodb
Mongo Age Group Aggregation
You were in the right place, but as $cond requires three arguments (being the evaluation , true result and false result) you need to "nest" these operations, which each subsequent $cond as the false condition. So your syntax here is a little off. You can also do this just in the $group to avoid passing through the whole collection with a separate $project. Based on the document structure you give

Categories : PHP
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