oracle四种连接查询

内连接(inner join)：连接两个表只要数据存在不匹配就都不显示。
外连接(outer join)：连接两个表存在空匹配的记录将都显示处理。
左连接(left join)：连接两个表以左表为显示表，显示左表匹配的NULL字段。
右连接(right join)：连接两个表以右表为显示表，显示右表匹配的NULL字段。

select t_card.card_num, t_card.password
  from t_card
  join t_member
    on t_card.member_id = t_member.id
 where t_card.card_num = 1480501452

 update t_card set t_card.password = '123456'
 where exists (select t_member.id
          from t_member
         where t_card.member_id = t_member.id
           and t_card.card_num = '1480501452')