oracle查询某表是否存在,某字段是否存在某表

查询某字段在某表中是否存在
select count(0) as aanum 
from user_tab_columns   
where UPPER(column_name)='SEQ_NO' AND TABLE_NAME = 'TEST_TABLE'

查询当前用户下是否存在某表OWNER为当前用户名称
select count(1) as bbnum from all_tables where TABLE_NAME = 'TEST_TABLE' and OWNER='select user from dual';