Information Schema
信息模式本身是一个名为information_schema的模式。这个模式自动存在于所有数据库中。信息模式由一组视图构成，它们包含定义在当前数据库中对象的信息。这个模式的拥有者是初始数据库用户，但是所有用户仅有使用权限，没有创建表、函数等对象的权限。
信息模式兼容PG，包括：constraint_table_usage, domain_constraints, domain_udt_usage, domains, enabled_roles, key_column_usage, parameters, referential_constraints, applicable_roles, administrable_role_authorizations, attributes, character_sets, check_constraint_routine_usage, check_constraints, collations, collation_character_set_applicability, column_domain_usage, column_privileges, column_udt_usage, columns, constraint_column_usage, role_column_grants, routine_privileges, role_routine_grants, routines, schemata, sequences, table_constraints, table_privileges, role_table_grants, tables, triggered_update_columns, triggers, udt_privileges, role_udt_grants, usage_privileges, role_usage_grants, user_defined_types, view_column_usage, view_routine_usage, view_table_usage, views, data_type_privileges, element_types, column_options, foreign_data_wrapper_options, foreign_data_wrappers, foreign_server_options, foreign_servers, foreign_table_options, foreign_tables, user_mapping_options, user_mappings, sql_features, sql_implementation_info, sql_languages, sql_packages, sql_parts, sql_sizing, sql_sizing_profiles。
下面章节只显示未在上述描述内的视图信息。
