---------------------------------------------------表操作-------------------------------------------------------
1．表的創(chuàng)建：
create table table_name(column_name datatype[,column_name datatype])
2．表數(shù)據(jù)的插入：
insert into table_name values(column_instance)
3．更新數(shù)據(jù)：
update table_name set column_instance=? where column_name=?
4．查詢數(shù)據(jù)：
select * from table_name where condition1 group by column_name1... having.... order by column_name[desc,[asc]]
5．刪除數(shù)據(jù)：
delete from table_name where column_name1=?
6．在表空間上建立表：
create table tablename(column_name,datatype)tablespace tablespace_name
7．oracle中提供5種約束：
Check，not null，unique，primary key，foreign key
(a)check約束
Create table policies(policy_id number ,holder_name varchar2(40),gender varchar2 (1) constraint chk_gender check (gender in ('M','F'),marital_status varchar2 (1),
date_of_birth date ,constraint chk_marital check (marital_status in('S','M','D','W')));
(b)not null約束
Create table policies(policy_id number ,holder_name varchar2 (40) not null,gender varchar2(1),marital_status varchar2(1),date_of_birth date not null);
對(duì)于not null的alter table語句與其他約束稍微有點(diǎn)不同。Alter table policies modify holder_name not null
(c)unique約束
create table emp(eid int ,ename varchar2(10),constraint uq unique(eid,ename))
create table emp (eid int ,ename varchar(10))
alter table emp add constraint pk primary key(eid,ename);
8。
(a)添加新列
alter table table_name add column_name datatype [constraint][constraint_name]
(b) 添加新列并指定默認(rèn)值
alter table table_name add column_name datatype default expression
alter table table_name drop column column_name--刪除列
alter table table_name modify column_name datatype--修改類屬性
alter table table_name disable constraint constraint_name--禁用約束
alter table table_name enable constraint constraint_name--啟用約束
alter table table_name add constraint constraint_name constraint_type(column_name)--添加約束
alter table table_name drop constraint constraint_name [cascade]--刪除約束
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alter table table_name add constraint constraint_name primary key (column_name, column_name...)