Question

My database is structured as follows:

{ title : "My First Post", author: "Jane",
  comments : [{ by: "Abe", text: "First" },
              { by : "Ada", text : "Good post" } ]
}

I am having trouble writing out the following:

• Get all posts on which Ada did not comment
• Get all posts on which Abe commented “First”
• Once a post has been found and stored in a post variable, display the text of the comment by Abe

Thanks.

Answer 1

Get all posts on which Ada did not comment

There is a $nin(stands for not in) operator in MongoDB you can write query like this:

db.my.collection.find({'comments.by': {$nin: ['Ada']}});

Get all posts on which Abe commented “First”

As far as comments are stored in array it’s absolutely legal to access particular items by their index. To achieve this goal you can write following query:

db.my.collection.find({'comments.0.by': 'Abe'});

Once a post has been found and stored in a post variable, display the text of the comment by Abe

This depends on your client application how you present retrieved data.