Which type of databases do not use a fixed schema?

Which type of databases do not use a fixed schema?

• A. Document databases
• B. Relational databases
• C. Non-relational databases
• D. Key/value databases

Answer: (C)

Databases that don’t require a fixed schema let each record have its own structure, giving you flexibility to store unstructured or evolving data. This is a defining trait of the non-relational family. In a document store, data is saved as documents that can vary in fields from one document to another, so you don’t need to define all fields upfront. A key-value store takes this even further: you retrieve values by a key, and the value can be any format or shape, with no enforced schema across the dataset. This schema-less nature makes it easy to adapt when data requirements change. Relational databases, by contrast, rely on a predefined schema with tables, columns, and data types that apply uniformly to all records, and changing that structure typically requires a formal schema migration. That contrast is why non-relational databases are the best match for a system that doesn’t use a fixed schema.

Databases that don’t require a fixed schema let each record have its own structure, giving you flexibility to store unstructured or evolving data. This is a defining trait of the non-relational family. In a document store, data is saved as documents that can vary in fields from one document to another, so you don’t need to define all fields upfront. A key-value store takes this even further: you retrieve values by a key, and the value can be any format or shape, with no enforced schema across the dataset. This schema-less nature makes it easy to adapt when data requirements change.

Relational databases, by contrast, rely on a predefined schema with tables, columns, and data types that apply uniformly to all records, and changing that structure typically requires a formal schema migration. That contrast is why non-relational databases are the best match for a system that doesn’t use a fixed schema.