select file_name from dba_temp_files where tablespace_name='TEMPSTUDENT_TABLESPACE';未选定行是啥意思?
2016-05-16
select constraint_name from user_constraints where table_name='USERINFO';
alter table userinfo
rename constraint pk_id to new_pk_id;
select constraint_name,status from user_constraints where table_name='USERINFO';
alter table userinfo
drop constraint new_pk_id;
alter table userinfo
rename constraint pk_id to new_pk_id;
select constraint_name,status from user_constraints where table_name='USERINFO';
alter table userinfo
drop constraint new_pk_id;
2016-05-10
create table userinfo_p1
(id number(6,0),
username varchar2(20),
userpwd varchar2(20),
constraint pk_id_username primary key(id,username));
select constraint_name from user_constraints where table_name='USERINFO_P1';
select constraint_name from user_constraints where table_name='USERINFO_P';
(id number(6,0),
username varchar2(20),
userpwd varchar2(20),
constraint pk_id_username primary key(id,username));
select constraint_name from user_constraints where table_name='USERINFO_P1';
select constraint_name from user_constraints where table_name='USERINFO_P';
2016-05-10
alter table userinfo
modify username varchar2(20) not null;
alter table userinfo
modify username varchar2(20) null;
modify username varchar2(20) not null;
alter table userinfo
modify username varchar2(20) null;
2016-05-10