Cosmos DB is a schemaless, document database that provides high performance, availability, and scalability. These features are not necessarily incompatible with a standards-compliant query language like SQL-92. In this section we will show various schemes that the adapter offers to bridge the gap with relational SQL and a document database.

The adapter models the schemaless Cosmos DB objects into relational tables and translates SQL queries into Cosmos DB queries to get the requested data. See Query Mapping (Sql API) for more details on how various Cosmos DB operations are represented as SQL.

The Automatic Schema Discovery scheme automatically finds the data types in a Cosmos DB object by scanning a configured number of rows of the object. You can use RowScanDepth, FlattenArrays, and FlattenObjects to control the relational representation of the collections in Cosmos DB. You can also write Free-Form Queries not tied to the schema.

Optionally, you can use Custom Schema Definitions to project your chosen relational structure on top of a Cosmos DB object. This allows you to define your chosen names of columns, their data types, and the location of their values in the collection.

Set GenerateSchemaFiles to save the detected schemas as simple configuration files that are easy to extend. You can persist schemas for all collections in the database or for the results of SELECT queries.