The DROP SCHEMA statement drops the specified schema from the database.
If you do not specify the RESTRICT or CASCADE keyword, all the objects associated with the specified schema_name must have been dropped prior to using this statement.
The RESTRICT keyword means that the schema is dropped only if all objects associated with the specified schema_name have been dropped prior to using this statement.
The CASCADE keyword means that all the database objects (such as tables) within the specified schema will be dropped automatically. If you use the CASCADE keyword and the objects in other schemas reference an object in the schema being dropped, those references will automatically be resolved by dropping those referencing objects or updating them to eliminate the reference.
Examples
DROP SCHEMA finance;
DROP SCHEMA finance CASCADE;
DROP SCHEMA finance RESTRICT;
DROP SCHEMA forecasting_db.securities_schema CASCADE;