Chapter 6. Collections

6.1. Collections Used Throughout This Book

Even though you can build your own JSON values with JSONiq by copying-and-pasting JSON documents, most of the time, your JSON data will be in a collection.

We now introduce collections, because collections are perfect to illustrate the JSON navigation syntax which will be introduced in the next section.

Collections are sequences of objects, identified by a name which is a string.

Adding or deleting collections from the set of known collections to a query processor, and loading the data in a collection are implementation-dependent and outside of the scope of this book.

We will just assume that there is a function named collection() that returns all objects associated with the provided collection name.

Example 6.1. Getting all objects from a collection.

collection("one-object")

Results:

{
  "question" : "What NoSQL technology should I use?"
}

6.1. Collections Used Throughout This Book

For illustrative purposes, we will assume that we have the following collections:

collection("one-object")
Example 6.2. The object in the one-object collection.
```
collection("one-object")
```
Results:
```
{
  "question" : "What NoSQL technology should I use?"
}
```

collection("faqs") - this is a collection of StackOverflow FAQs.

Example 6.3. One object from the faqs collection.

collection("faqs")[1]

Results:

{
  "_id" : "511C7C5C9A277C22D138802D",
  "question_id" : 4419499,
  "last_edit_date" : "2012-12-17T00:02:31",
  "creation_date" : "2010-12-11T23:15:19",
  "last_activity_date" : "2012-12-17T00:02:31",
  "score" : 15,
  "accepted_answer_id" : 4421601,
  "title" : "MySQL and NoSQL: Help me to choose the right o
ne",
  "tags" : [ "php", "mysql", "nosql", "cassandra" ],
  "view_count" : 3972,
  "owner" : {
    "user_id" : 279538,
    "display_name" : "cedivad",
    "reputation" : 430,
    "user_type" : "registered",
    "profile_image" : "http://www.gravatar.com/avatar/b77fa
dd2ba791134ac40a9c184be1eda?d=identicon&amp;r=PG",
    "link" : "http://stackoverflow.com/users/279538/cedivad
",
    "accept_rate" : 74
  },
  "link" : "http://stackoverflow.com/questions/4419499/mysq
l-and-nosql-help-me-to-choose-the-right-one",
  "is_answered" : true
}

collection("answers") - this is a collection of StackOverflow answers (to the previous FAQs).

Example 6.4. One object from the answers collection.

collection("answers")[1]

Results:

{
  "_id" : "511C7C5D9A277C22D13880C3",
  "question_id" : 37823,
  "answer_id" : 37841,
  "creation_date" : "2008-09-01T12:14:38",
  "last_activity_date" : "2008-09-01T12:14:38",
  "score" : 7,
  "is_accepted" : false,
  "owner" : {
    "user_id" : 2562,
    "display_name" : "Ubiguchi",
    "reputation" : 1871,
    "user_type" : "registered",
    "profile_image" : "http://www.gravatar.com/avatar/00b87
a917ec763c0c051dc6b8c06f402?d=identicon&amp;r=PG",
    "link" : "http://stackoverflow.com/users/2562/ubiguchi"

  }
}

Many queries in this book can be directly input into 28.io's try-it-now sandbox, as these collections are preloaded (this is real-world data).