Databases can decide up-front how prescriptive they want to be about specifying a schema for the data.
When NoSQL databases came to the fore a decade ago, a key point was that they didn't require a schema. The schema could be encoded and enforced in the application rather than in the database. It was thought that schemas were a hindrance in dealing with all of the semi structured data that was getting produced in modern enterprise. So because the early NoSQL systems didn't have a type system, they didn't enforce the standard that all rows in the table have the same structure, they didn't enforce a whole lot.
However, today, most of these NoSQL databases have acquired an SQL interface. Most of them ...
