oracle夜未眠之一增删改查

1、创建一个表，同时插入一些数据

create table empTemp as select *  from emp where sal>1000;

2、清空表数据

truncate table empTemp;

3、删除表

drop table empTemp;

4、增加表的字段

alter table empTemp add tempName varchar2(50);

5、修改字段

alter table empTemp tempName varchar2(10);

alter table empTemp column rename tempName  to tempName2;

6、删除字段

alter tabel empTemp  drop column tempName2;

7、重命名表

rename empTemp  to empTemp_Table;

8、insert 语句

insert into empTemp(id,name) select id,name from emp where age>18;

9、update语句

update empTemp set(name,age)=(select name,age from emp where id='1');

10、牛X的merge,联想到了hibernate

create tabel temp_t1(id varchar2(100) not NULL PRIMARY key,name varchar2(50) NOT Null);

create tabel temp_t2(id varchar2(100) not NULL PRIMARY key,name varchar2(50) NOT Null);

insert into temp_t1(id,name) values('1','test1');

insert into temp_t1(id,name) values('2','test2');

merge into temp_t2

using temp_t1

on(temp_t1.id=temp_t2.id)

when matched then

update set temp_t2.name=temp_t1.name

when not matched then

insert(id name) values(temp_t1.id,temp_t1.name);

二、约束

PRIMARY key:主键约束，不能有重复值，不能为空

not null:非空约束

unique:不能重复，但是可以有多个null值

check:插入值的约束 age number check(age between 0 and 18 ),

三、外键

fid NUMBER REFERENCES jf_applymain(fid) ON DELETE cascade,

或

CONSTRAINT temp_fid_fk FOREIGN KEY(fid) REFERENCES jf_applymain(fid);

四、已经建立好的表如何使用如上约束，stu(id,name);

--增加主键
ALTER TABLE stu ADD CONSTRAINT stu_id_pk PRIMARY KEY(ID);
--增加唯一约束
ALTER TABLE stu ADD CONSTRAINT stu_name_unique unique(NAME);
--增加其他约束
ALTER TABLE stu ADD CONSTRAINT stu_age_check check(age BETWEEN 0 AND 18);
--增加主外键约束，带练级删除
ALTER TABLE stu ADD CONSTRAINT stu_id_pk PRIMARY KEY(ID) REFERENCES jf_applymain(fid) ON DELETE CASCADE;

--删除约束

ALTER TABLE stu DROP CONSTRAINT stu_id_pk;
ALTER TABLE stu DROP CONSTRAINT stu_name_unique;

--启用约束
ALTER TABLE stu ENABLE CONSTRAINT stu_name_unique;

--禁用约束
ALTER TABLE stu DISABLE CONSTRAINT stu_name_unique;