What is it

From architectural layer perspective, database is an abstraction of structures of data.

• comes with hard boundary separation and restrictive definitions.
  • restrictive definitions prevent users from misusing the database.
    • restrictive definitions make behaviors concrete (predictable as expected).
  • boundary separation allows database layer to be easily swapped out (much like dependency injection).
• It supplies a lot out of the box.
  • querying language
  • optimizations
  • other idiomatic behaviors