--一共查出了13条数据
select * from user_tab_columns where rownum < 22 and table_name like '%MS_PERMISSION%'

--下面的sql本来可以查出我想要的，可是一共只查出了5条数据，怎么少了8条
select u.*,t.POSITION as PK from USER_COL_COMMENTS u left join user_cons_columns t on u.column_name = t.column_name
where u.table_name like '%MS_PERMISSION%' and u.column_name like '%%' and u.table_name = t.table_name
order by u.table_name,t.POSITION

SELECT U.*, T.POSITION AS PK
  FROM USER_COL_COMMENTS U
 RIGHT JOIN USER_CONS_COLUMNS T
    ON U.COLUMN_NAME = T.COLUMN_NAME
   AND U.TABLE_NAME = T.TABLE_NAME
   AND U.TABLE_NAME LIKE '%MS_PERMISSION%'
   AND U.COLUMN_NAME LIKE '%%'
 ORDER BY U.TABLE_NAME, T.POSITION;

------解决方案--------------------
你的条件全是注释表的条件，自然全被过滤掉了，把条件全改成主表user_tab_cols的条件