多项选择题
A.seq_page_cost B.enable_indexscan C.random_page_cost D.enable_indexonlyscan
A.CREATE B.DROP C.DELETE D.USAGE
A.直接执行DROP USER app_r; B.先执行DROP OWNED BY app_r;再执行DROP USER app_r; C.先执行REASSIGN OWNED BY app_rTOsystem;再执行DROP USER app_r; D.直接执行DROP ROLE app_r CASCADE;