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20.4.4 Documents and Collections

In MySQL, collections contain JSON documents that you can add, find, update, and remove. Collections are containers within a schema that you create, list, and drop.

The examples in this section use the countryinfo collection in the world_x database. For instructions on setting up the world_x database sample, see Section 20.4.2, “Import Database Sample”.

Documents

In MySQL, documents are represented as JSON objects. Internally, they are stored in an efficient binary format that enables fast lookups and updates.

  • Simple document format for Python:

    {"field1": "value", "field2" : 10, "field 3": null}
    

An array of documents consists of a set of documents separated by commas and enclosed within [ and ] characters.

  • Simple array of documents for Python:

    [{"Name": "Aruba", "_id": "ABW"}, {"Name": "Angola", "_id": "AGO"}]
    

MySQL supports the following Python value types in JSON documents:

  • numbers (integer and floating point)

  • strings

  • boolean (False and True)

  • None

  • arrays of more JSON values

  • nested (or embedded) objects of more JSON values

Collections

Collections are containers for documents that share a purpose and possibly share one or more indexes. Each collection has a unique name and exists within a single schema.

The term schema is equivalent to a database, which means a group of database objects (as opposed to relational schema used to enforce structure and constraints over data). A schema does not enforce conformity on the documents in a collection.

In this quick-start guide:

  • Basic objects include:

    Object form Description
    db db is a global variable assigned to the current active schema.
    db.get_collections() db.get_collections() holds a list of collections in the schema. Use the list to get references to collection objects, iterate over them, and so on.
  • Basic operations scoped by collections include:

    Operation form Description
    db.name.add() The add() method inserts one document or a list of documents into the named collection.
    db.name.find() The find() method returns some or all documents in the named collection.
    db.name.modify() The modify() method updates documents in the named collection.
    db.name.remove() The remove() method deletes one document or a list of documents from the named collection.

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