2017-07-17（表的创建，修改）

create table wgb
(name varchar(10),
age number(3),
job varchar2(5),
birthday date,
sex char(1)
);
select * from wgb;
alter table wgb
add (description varchar2(20));
alter table wgb
add (description1 varchar2(20));
alter table wgb
modify (sex char(5));
alter table wgb
modify (description varchar2(40));
alter table wgb
modify (age number(5));
insert into wgb(name, age, job, birthday, sex, description)
values('刘德华', 51, 'actor', to_date('2001-5-10','yyyy-mm-dd'), 'man', '他是一个歌手同时也是一个演员'
)
insert into wgb007(name, age, job, birthday, description)
values('刘喜', 1500, '东厂', to_date('1523-5-10','yyyy-mm-dd'), '他是一个男人同时也是一个女人'
)
insert into wgb(name, age, job, birthday, sex, description)
values('乔峰', 1600, '帮主', to_date('1423-5-10','yyyy-mm-dd'), 'man', '他是一个高手同时也是一个演员'
)
alter table wgb
drop column description1
rename wgb to wgb007
rename wgb to wgb008
rename wgb to wgb009
select * from wgb007;
select * from wgb008;
select * from wgb007;
alter table wgb007
modify ( age number(5) not null)
insert into wgb007(name, age, job, birthday, sex, description)
values('乔峰爸', 1622， '帮主', to_date('1423-5-10','yyyy-mm-dd'), 'man', '他是一个高手同时也是一个演员'
)
alter table wgb007
drop CONSTRAINT SYS_C009666
alter table wgb007
add(primary key(name))

delete table

drop table wgb;

 

CREATE TABLE employees(
employee_id NUMBER(6),
first_name VARCHAR2(20),

job_id VARCHAR2(10) NOT NULL,
CONSTRAINT em_em_id_pk
PRIMARY KEY (EMPLOYEE_ID));

select * from employees;
insert into employees (employee_id,first_name,job_id)
values(12,'dfsg',23)
insert into employees (employee_id,first_name,job_id)
values(1,'dfsg',23)
drop table employees;

CREATE TABLE employees(
employee_id NUMBER(6),
first_name VARCHAR2(20),

job_id VARCHAR2(10) NOT NULL,

PRIMARY KEY (EMPLOYEE_ID)
);