What the Heck Are Document Databases?

Related Data in a Single Record

A lot of people incorrectly presume that nonrelational databases are flat files. The documents stored in a document database are capable of containing shaped data: trees with nodes. Each record in the database is a document and can be an autonomous set of data. It’s self-describing—including its possibly unique schema—and isn’t necessarily dependent on any other document.

Following is a typical example of what a record might look like in a document database (I’ll steal a sample from the MongoDB tutorial that represents a student):

{
"name" : "Jim",
"scores" : [ 75, 99, 87.2 ]
}

And here’s one from the CouchDB introductory article, which describes a book:

{
"Subject": "I like Plankton"
"Author": "Rusty"
"PostedDate": "5/23/2006"
"Tags": ["plankton", "baseball", "decisions"]
"Body": "I decided today that I don't like baseball. I like plankton."
}

These are simple structures with string data, numbers and arrays. You can also embed objects within objects for a more complex document structure, such as this blog post example:

{
"BlogPostTitle”: “LINQ Queries and RavenDB”,
"Date":"\/Date(1266953391687+0200)\/",
"Content":”Querying RavenDB is very familiar for .NET developers who are already
using LINQ for other purposes”,
"Comments":[
{
"CommentorName":"Julie",
"Date":"\/Date(1266952919510+0200)\/",
"Text":"Thanks for using something I already know how to
work with!",
"UserId":"users/203907"
},
]
}

via Data Points – What the Heck Are Document Databases?.