增删改查，导入导出

增加约束

LIKE 模糊查询

alter table   add constraint  check()

alter table  dept add constraint fk_   foreign key()  reference  emp(..)

union --可以插入多条数据

 

删

delete from ...where   

truncate table  .....    (清空)

select distinct  deptno  from emp (消除重复的行)

 

 

改

update .... set ...   where  ...

create sysnonym ....for ...

drop sysnonym....

 

 exp scott/abc file=employ.dmp tables=(emp,dept);

 imp sys/abc file=emoploy.dmp fromuser=scott touser=sys commit=y;