第26次活动：2017-10-23（星期一晚上7:00-9:30）
selecttable_name from user_tables order by 1 desc;create table t05110_t ( anumber ) ;
alter table t05110_t add(b varchar2(20) ,c date );
alter table t05110_t modify (c number ) ;
insert into t05110_t values ( 1, 'A', 10) ;
---alter table t05110_t modify (c varchar2(20)) ;
alter table t05110_t modify (b char(21)) ;
--------------------------
alter table t05110_t drop columnb;
alter table t05110_t add ( b number, d number ,e number ) ;
select * from t05110_t;
alter table t05110_t drop ( a,e ) ;
select * from t05110_t;
--------
alter table t05110_t setunusedcolumnc ;
----
select*from dict where table_name like '%UNUSED%';
select* from user_unused_col_tabs;
---
alter tablet05110_tdrop unused columns;
-----
alter table t05110_t rename column b to bb;
-----
rename t05110_t to t05110_t1;
select * fromt05110_t1;
alter table t05110_t1 read only;
insert intot05110_t1 values (1,11);
alter table t05110_t1 read write;
insert intot05110_t1 values (1,11);
-----
createor replaceview v1 as
select e.employee_id,e.last_name,e.email,e.department_id, d.department_name
from employees e, departments d
where e.department_id=d.department_id order by 1;
select* from v1;
update v1 set email='XXX' where email='SKING';
update v1 setdepartment_id=60 where employee_id=100;
update v1 setdepartment_name='YYY' where email='XXX';
create table t05111_a( anumber ) ;
create view v2 as select a*2b from t05111_a;
insert into t05111_a values (8) ;
select* from v2;
update v2 set b=10 ;
---
CREATE or replace VIEW empvu80
AS SELECTemployee_id, last_name, salary , department_id
FROM employees
WHERE department_id = 80order by employee_id
with check option constraint v2_chk;
----
select* fromempvu80;
update empvu80 setdepartment_id=60 where employee_id=145;
select* from user_constraintsorder by table_name;
update empvu80 setdepartment_id=60 where employee_id=146;
select* from seq[ DISCUZ_CODE_5 ]nbsp; order by 1 desc;
select* from dba_sequencess where s.sequence_owner='HR'
and s.sequence_name like 'SEQ%';
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