1  –  CASCADE

    Deletes all other definitions (views, constraints, tables,
    sequences, indexes, and triggers) that refer to the named schema
    and then deletes that schema definition. This is known as a
    cascading delete.

    If you specify the CASCADE keyword, SQL deletes all definitions
    contained by the schema before deleting the schema.

    If you do not specify the CASCADE keyword, the schema must be
    empty.

2  –  IF_EXISTS

    Prevents SQL command language from displaying error messages if
    the referenced object does not exist in the database.

3  –  RESTRICT

    Returns an error message if other definitions refer to the named
    schema. The DROP SCHEMA RESTRICT statement will not delete a
    schema until you have deleted all other definitions that refer to
    the named schema. The DROP SCHEMA statement specifies an implicit
    RESTRICT by default.

4  –  schema-name

    Specifies the schema name. You must qualify the schema name with
    catalog and alias names if the schema is not in the default
    catalog and database. For more information about schema names,
    see the User_Supplied_Names HELP topic.