设有一数据库，包括四个表：学生表（Student）、课程表（Course）、成绩表（Score）以及教师信息表（Teacher）。四个表的结构分别如表1-1的表（一）~表（四）所示，数据如表1-2的表（一）~表（四）所示。用SQL语句创建四个表并完成相关题目。

-- Create table
create table STUDENT
(
  sno       VARCHAR2(3) not null,
  sname     VARCHAR2(8) not null,
  ssex      VARCHAR2(2) not null,
  sbirthday DATE,
  class     VARCHAR2(5)
)
tablespace USERS
  pctfree 10
  initrans 1
  maxtrans 255;
-- Add comments to the table 
comment on table STUDENT
  is ‘学生表‘;
-- Add comments to the columns 
comment on column STUDENT.sno
  is ‘学号（主键）‘;
comment on column STUDENT.sname
  is ‘学生姓名‘;
comment on column STUDENT.ssex
  is ‘学生性别‘;
comment on column STUDENT.sbirthday
  is ‘学生出生年月‘;
comment on column STUDENT.class
  is ‘学生所在班级‘;

-- Create table
create table COURSE
(
  cno   VARCHAR2(5) not null,
  cname VARCHAR2(10) not null,
  tno   VARCHAR2(3) not null
)
tablespace USERS
  pctfree 10
  initrans 1
  maxtrans 255;
-- Add comments to the table 
comment on table COURSE
  is ‘课程表‘;
-- Add comments to the columns 
comment on column COURSE.cno
  is ‘课程号（主键）‘;
comment on column COURSE.cname
  is ‘课程名称‘;
comment on column COURSE.tno
  is ‘教工编号（外键）‘;

-- Create table
create table SCORE
(
  sno    VARCHAR2(3) not null,
  cno    VARCHAR2(5) not null,
  degree NUMBER(4,1)
)
tablespace USERS
  pctfree 10
  initrans 1
  maxtrans 255;
-- Add comments to the table 
comment on table SCORE
  is ‘成绩表‘;
-- Add comments to the columns 
comment on column SCORE.sno
  is ‘学号（外键）‘;
comment on column SCORE.cno
  is ‘课程号（外键）‘;
comment on column SCORE.degree
  is ‘成绩‘;

-- Create table
create table TEACHER
(
  tno       VARCHAR2(3) not null,
  tname     VARCHAR2(4) not null,
  tsex      VARCHAR2(2) not null,
  tbirthday DATE,
  prof      VARCHAR2(6),
  depart    VARCHAR2(10) not null
)
tablespace USERS
  pctfree 10
  initrans 1
  maxtrans 255;
-- Add comments to the table 
comment on table TEACHER
  is ‘教师表‘;
-- Add comments to the columns 
comment on column TEACHER.tno
  is ‘教工编号（主键）‘;
comment on column TEACHER.tname
  is ‘教工姓名‘;
comment on column TEACHER.tsex
  is ‘教工性别‘;
comment on column TEACHER.tbirthday
  is ‘教工出生年月‘;
comment on column TEACHER.prof
  is ‘职称‘;
comment on column TEACHER.depart
  is ‘教工所在部门‘;