What are the main characteristics of NOSQL systems in the areas related to data models and query languages?

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CHARACTERISTICS RELATED TO DATA MODELS AND QUERY LANGUAGES.

 1. Not Requiring a Schema:

  •  Allowing semi-structured and self-describing data.
  • The users can specify a partial schema in some systems to improve storage efficiency, but it is not required to have a schema in most of the NoSQL systems. 
  • Constraints on the data would have to be programmed in the application programs that access the data items. 
  • Languages for describing semi-structured data: JSON (JavaScript Object Notation) and XML (Extensible Markup Language)

2.  Less Powerful Query Languages: 

  •  Many applications that use NoSQL systems may not require a powerful query language such as SQL, because search (read) queries in these systems often locate single objects in a single file based on their object keys. 
  • Reading and writing the data objects is accomplished by calling the appropriate operations by the programmer (API).
  •  SCRUD: Search, Create, Read, Update and Delete
  • Provide a high-level query language, but it may not have the full power of SQL, for example, the joins need to be implemented in the application programs.

3. Versioning: 

  • Provide storage of multiple versions of the data items, with the timestamps of when the data version was created.


Characteristics of NoSQL:

  • It’s more than rows in tables—NoSQL systems store and retrieves data from many formats: key-value stores, graph databases, column-family (Bigtable) stores, document stores, and even rows in tables.
  • It’s free of joins—NoSQL systems allow you to extract your data using simple interfaces without joins.
  • It’s schema-free—NoSQL systems allow you to drag and drop your data into a folder and then query it without creating an entity-relational model.
  • It works on many processors—NoSQL systems allow you to store your database on multiple processors and maintain high-speed performance.
  • It uses shared-nothing commodity computers—Most (but not all) NoSQL systems leverage low-cost commodity processors that have separate RAM and disk.
  • It supports linear scalability—When you add more processors, you get a consistent increase in performance.
  • It’s innovative—NoSQL offers options for a single way of storing, retrieving, and manipulating data. NoSQL supporters (also known as NoSQLers) have an inclusive attitude about NoSQL and recognize SQL solutions as viable options. To the NoSQL community, NoSQL means “Not only SQL.”


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