How do I do a "NOT IN" query in Mongo?

Question

This is my document:

{      title:"Happy thanksgiving",     body: "come over for dinner",     blocked:[        {user:333, name:'john'},        {user:994, name:'jessica'},        {user:11, name: 'matt'},     ] } 

What is the query to find all documents that do not have user 11 in "blocked"?

Answer 1

You can use $in or $nin for "not in"

Example ...

> db.people.find({ crowd : { $nin: ["cool"] }}); 

I put a bunch more examples here: http://learnmongo.com/posts/being-part-of-the-in-crowd/

Answer 2

Since you are comparing against a single value, your example actually doesn't need a NOT IN operation. This is because Mongo will apply its search criteria to every element of an array subdocument. You can use the NOT EQUALS operator, $ne, to get what you want as it takes the value that cannot turn up in the search:

db.myCollection.find({'blocked.user': {$ne: 11}}); 

However if you have many things that it cannot equal, that is when you would use the NOT IN operator, which is $nin. It takes an array of values that cannot turn up in the search:

db.myCollection.find({'blocked.user': {$nin: [11, 12, 13]}});