introduction to nosql as you've readthe goal of nosql databases isn' only to offer way to partition databases successfully over multiple nodesbut also to present fundamentally different ways to model the data at hand to fit its structure to its use case and not to how relational database requires it to be modeled to help you understand nosqlwe're going to start by looking at the core acid principles of single-server relational databases and show how nosql databases rewrite them into base principles so they'll work far better in distributed fashion we'll also look at the cap theoremwhich describes the main problem with distributing databases across multiple nodes and how acid and base databases approach it acidthe core principle of relational databases the main aspects of traditional relational database can be summarized by the concept acidatomicity--the "all or nothingprinciple if record is put into databaseit' put in completely or not at all iffor instancea power failure occurs in the middle of database write actionyou wouldn' end up with half recordit wouldn' be there at all consistency--this important principle maintains the integrity of the data no entry that makes it into the database will ever be in conflict with predefined rulessuch as lacking required field or field being numeric instead of text isolation--when something is changed in the databasenothing can happen on this exact same data at exactly the same moment insteadthe actions happen in serial with other changes isolation is scale going from low isolation to high isolation on this scaletraditional databases are on the "high isolationend an example of low isolation would be google docsmultiple people can write to document at the exact same time and see each other' changes happening instantly traditional word documenton the other end of the spectrumhas high isolationit' locked for editing by the first user to open it the second person opening the document can view its last saved version but is unable to see unsaved changes or edit the document without first saving it as copy so once someone has it openedthe most up-to-date version is completely isolated from anyone but the editor who locked the document durability--if data has entered the databaseit should survive permanently physical damage to the hard discs will destroy recordsbut power outages and software crashes should not acid applies to all relational databases and certain nosql databasessuch as the graph database neo we'll further discuss graph databases later in this and in for most other nosql databases another principle appliesbase to understand base and why it applies to most nosql databaseswe need to look at the cap theorem