NoSQL databases

  • This storage system stands for Not only SQL (structured query language).
  • SQL queries cannot be used to access those databases.
  • The goal is to fulfill the requirements of big data: scalability, availability and performance.
  • More pragmatically, it allows to increase server storage increase (horizontal scalability) and maintenance of performance through a faster retrieval of the data.
  • Again SQL cannot be used to query these databases. There are 4 types of non relational or No-SQL databases (It can be seen as a structured method for accessing what is being searched):
    • key-value: for a given term there is a number or associations (value) which can contain multiple amounts of data.
    • column-based
    • document
    • graph (popular with social media): the information is stored in nodes and the relations are mentioned (for example network of friends of an individual)


  • The objective is to add horizontal scalability to the performance of a relational model.
  • It combines the performance NoSQL and accessibility of relational databases models (see Storing Data: ACID)

Reference: Big Data: A very short introduction by Dawn E. Holmes. Oxford University Press, 2017


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