To support SQL access to Apache Cassandra, the driver maps the Cassandra data model to a relational schema. This process involves the normalization of complex types. You may need to be familiar with the normalization of complex types to formulate SQL queries correctly. The driver handles the normalization of complex types in the following manner:
If collection types (Map, List, and Set) are discovered, the driver normalizes the Cassandra table into a set of parent-child tables. Primitive types are mapped to a parent table, while each collection type is mapped to a child table that has a foreign key relationship to the parent table.
Non-nested Tuple and user-defined types (also referred to as Usertype) are flattened into a parent table alongside primitive types.
Any nested complex types (Tuple, user-defined types, Map, List, and Set) are exposed as JSON-style strings in the parent table.
The normalization of complex types is described in greater detail in the following topics.
If collection types (Map, List, and Set) are discovered, the driver normalizes the Cassandra table into a set of parent-child tables. Primitive types are mapped to a parent table, while each collection type is mapped to a child table that has a foreign key relationship to the parent table.
