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What is JSON an abbreviation for?
JSON objects can have object IDs.
False
What are the key-value pairs in JSON objects?
attribute name and value
JSON is widely used for data exchange in modern applications, especially in _______________ services.
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What is the type of data structure used to store multiple values in JSON?
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SQL extensions are not available for JSON data types.
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Match the JSON data type with its description:
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What is the main advantage of using semi-structured data in data exchange?
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XML is a relatively new notation for semi-structured data.
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What are some examples of semi-structured data models?
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XML stands for ______________________ Markup Language.
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Why may the relational model's requirement of atomic data types be an overkill in some applications?
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Match the following semi-structured data models with their characteristics:
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What is a characteristic of semi-structured data models?
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JSON is a document format.
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What is the purpose of JSON_agg aggregate function in PostgreSQL?
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In JSON, character encoding is strictly _______________.
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Match the following data types with their descriptions:
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JSON has namespaces.
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What is an example of an array database?
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In JSON, the _______________ function is used to generate JSON from relational data.
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What is the purpose of an object-relational mapping (ORM) system?
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What is a characteristic of JSON?
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Study Notes
JSON
- JSON is a minimal, textual, language-independent representation widely used for data exchange.
- It is a notation for representing data in a format that is easy for humans to read and write.
- JSON is versionless and does not have namespaces, it uses context to avoid ambiguity.
- Character encoding is strictly Unicode.
- JSON is not a document format and is not a markup language.
Generating JSON from Relational Data
- JSON can be generated from relational data using object-relational mapping.
- Example: json.build_object(‘ID’, 12345, ‘name’, ‘Einstein’)
- JSON collections can be created using aggregation functions such as json_agg in PostgreSQL.
Semi-Structured Data Models
- Semi-structured data models have flexible schemas, allowing each tuple to have a different set of attributes.
- They support multivalued data types, such as sets, multisets, and key-value maps.
- Examples: set of interests {‘basketball, ‘La Liga’, ‘cooking’, ‘anime’, ‘jazz’}, key-value map {(brand, Apple), (ID, MacBook Air), (size, 13), (color, silver)}.
- Operations on maps: put(key, value), get(key), delete(key).
Arrays
- Arrays are widely used for scientific and monitoring applications.
- Examples: readings taken at regular intervals can be represented as an array of values instead of (time, value) pairs.
- Array databases provide specialized support for arrays, such as compressed storage and query language extensions.
- Examples of array databases: Oracle GeoRaster, PostGIS, SciDB.
Object-Relational Data Model
- The object-relational data model provides a richer type system with complex data types and object orientation.
- Applications are often written in object-oriented programming languages, which do not match the relational type system.
- Approaches for integrating object-orientation with databases include:
- Building an object-relational database by adding object-oriented features to a relational database.
- Automatically converting data between programming language models and relational models using object-relational mapping.
- Building an object-oriented database that natively supports object-oriented data and direct access from programming languages.
Object-Relational Database Systems
- User-defined types can be created using object-relational database systems.
- Table types can be created using array and multiset data types.
- Example: create type Person (ID varchar(20) primary key, name varchar(20), address varchar(20)) ref from(ID); create table people of Person;
Type and Table Inheritance
- Type inheritance allows for the creation of new types based on existing types.
- Example: create type Student under Person (degree varchar(20)); create type Teacher under Person (salary integer);
- Table inheritance syntax in PostgreSQL and Oracle: create table students (degree varchar(20)) inherits people; create table teachers (salary integer) inherits people;
Reference Types
- Creating reference types: create type Person (ID varchar(20) primary key, name varchar(20), address varchar(20)) ref from(ID); create table people of Person;
- Using references in path expressions: select head->name, head->address from departments;
Object-Relational Mapping
- Object-relational mapping (ORM) systems allow for the specification of mapping between programming language objects and database tuples.
- Automatic creation of database tuples upon creation of objects.
- Automatic update/delete of database tuples when objects are updated/deleted.
- Interface to retrieve objects satisfying specified conditions.
- Examples: Hibernate ORM for Java, Django ORM for Python.
XML
- XML: Extensible Markup Language.
- Earlier generation notation, still used extensively.
- XML uses tags to mark up text.
- Example: Intro.to Computer Science “..” specifies the parent.doc(name) returns the root of a named document.
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Description
This quiz covers the basics of JSON, including its features, versions, and how it is used to represent data. It also touches on generating JSON from relational data.
