Key concepts for the Java API for JSON

JSON namespaces

Each JSON data store can support multiple JSON namespaces. JSON namespaces are conceptually similar to a MongoDB database and are represented as an SQL schema. By default, the namespaces are not case-sensitive.

In the command-line interface, the namespace is set with the use command and referenced with the command prefix db.

nosql>use media
Switched to schema MEDIA
nosql>db.getCollectionNames()
[movies, books, audio]

JSON collections

A JSON collection is a named grouping of JSON documents. Document structures in a collection might differ significantly. However, usually documents in a collection are of a similar nature to enable finding and grouping data.

Collections are represented in a Db2 table with a custom-defined or automatically generated unique identifier and a binary large object to hold the semi-structured document content. A collection can be created explicitly with the createCollection() command. A collection is implicitly created when an insert is attempted for a collection that did not previously exist.

The document identifiers that serve as primary key must be of the same data type for all documents in the collection.

JSON documents

JSON documents consist of fields, which are name-value pair objects. The fields can be in any order, and be nested or arranged in arrays.

There is no enforcement of document structures. Therefore, other documents in the same collection might have a subset of fields, extra fields, or different representations of the same field.

For Date string values, the client converts the value to UTC to be stored in Db2 databases. It is also retrieved as a Date in UTC format.

The following example represents a sample JSON document:

{
	name:"Joe",
	age:25,
	phone:["555-666-7777", "444-789-1234"],
	homeAddress:
		{street:"Sycamore Avenue",
		city: “Gilroy”,
		zipcode:"95046"
		}
	businessAddress:
		{
		street:"Bailey Avenue",
		City: “San Jose”,
		zipcode:"95141"
		}
}

JSON nested objects

JSON objects can be nested inside other JSON objects. Each nested object must have a unique access path.

The same field name can occur in nested objects in the same document. However, uniqueness must still apply for the full access name.

To access nested fields, concatenate the field names that are separated by a . (dot). For example, use author.lastname to access the surname for the author in this document:

{"isbn": "123-456-222",  
 "author": 
    {
      "lastname": "Doe",
      "firstname": "Jane"
    },
"editor": 
    {
      "lastname": "Smith",
      "firstname": "Jane"
    },
  "title": "The Ultimate Database Study Guide",  
  "category": ["Non-Fiction", "Technology"]
 }

In the example, the field name lastname occurs in the author and the editor object. The prefixes in author.lastname and editor.lastname provide unique access.