MongoDB is not equal

Question

I'm trying to display a query in MongoDB where the text field is not '' (space)

{ 'name' : { $not : '' }} 

However, I get an invalid use of $not error

I looked through the documentation, but the examples that they use are for complex cases (with regexp and $not negating another statement).

How do I do the simple thing I'm trying to do?

Answer 1

$ne - $not should be followed by the standard operator:

Examples for $ne , which means not equal:

 use test switched to db test db.test.insert({author : 'me', post: ""}) db.test.insert({author : 'you', post: "how to query"}) db.test.find({'post': {$ne : ""}}) { "_id" : ObjectId("4f68b1a7768972d396fe2268"), "author" : "you", "post" : "how to query" } 

And now $not , which takes the predicate ( $ne ) and negates it ( $not ):

 db.test.find({'post': {$not: {$ne : ""}}}) { "_id" : ObjectId("4f68b19c768972d396fe2267"), "author" : "me", "post" : "" } 

Answer 2

If you want to make some $ne , then do

 db.users.find({name : {$nin : ["mary", "dick", "jane"]}}) 

Answer 3

Use $ne instead of $not

http://docs.mongodb.org/manual/reference/operator/ne/#op._S_ne

 db.collections.find({"name": {$ne: ""}}); 

Answer 4

From Mongo docs :

The $not operator affects only other operators and cannot check fields and documents. So, use the $not operator for logical clauses and the $ne operator to check the contents of a field.

Since you are testing the field directly with $ne , this is the correct statement to use here.

Edit:

The situation in which you would like to use $not :

 db.inventory.find( { price: { $not: { $gt: 1.99 } } } ) 

This will select all documents where:

• The value of the price field is less than or equal to 1.99 or the price
• Field does not exist

Answer 5

If the array has null and you want to avoid it:

 db.test.find({"contain" : {$ne :[] }}).pretty() 

Answer 6

Real life example; find all but the current user:

 var players = Players.find({ my_x: player.my_x, my_y: player.my_y, userId: {$ne: Meteor.userId()} });