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What is the difference between a Relational and Non-Relational Database?

MySQL, PostgreSQL and MS SQL Server are relational database systems, and NoSQL, MongoDB, etc. are non-relational DBMSs.

What are the differences between the two types of system?

Solution

  • Relational databases have a mathematical basis (set theory, relational theory), which are distilled into SQL == Structured Query Language.

    NoSQL's many forms (e.g. document-based, graph-based, object-based, key-value store, etc.) may or may not be based on a single underpinning mathematical theory. As S. Lott has correctly pointed out, hierarchical data stores do indeed have a mathematical basis. The same might be said for graph databases.

    I'm not aware of a universal query language for NoSQL databases.