0729 操作符及SQL函数

select empno,ename,job,sal+1000 from emp

-- 比较运算符   between and   包头不包尾
select * from emp where sal between 1000 and 2000

select * from emp where comm is not null

SELECT *  FROM t_student
WHERE sbirthday >= ‘01-1月-90‘ 
AND not sclass = 2;
SELECT *  FROM t_student
WHERE sbirthday >= ‘01-1月-90‘ 
AND sclass <> 2;
SELECT *  FROM t_student
WHERE sbirthday >= ‘01-1月-90‘ 
AND sclass != 2;

select empno,sal +nvl(comm,0)as sal from emp;

select ename,sal+nvl2(comm,10000,0) from emp

select nullif(200,200) from dual;

select empno,ename,job,sal,rank() over(order by sal desc) as numm from emp

-- 同义词 创建用户 这里要切换 管理员登录
CREATE  USER  test  IDENTIFIED  BY 123456;
GRANT  CONNECT , CREATE  SYNONYM TO test;
GRANT  SELECT   ON   SCOTT.EMP  TO test;
GRANT  DELETE  ON   SCOTT.EMP TO test;
GRANT  UPDATE  ON  SCOTT.EMP TO test;
-- 以test身份登录
select * from scott.emp;
-- 创建同义词 synonym  谁建的谁用  
create synonym staff for scott.emp;
select * from staff

-- 以sys或system身份登录  创建公有同义词
create public synonym emps for scott.emp 

-- 创建序列 先切换用户 scott
create sequence seq_student
start with 1
increment by 1;

-- 实现自增的功能 :利用里面的值  
insert into stu values(seq_student.nextval,‘袁一鸣‘);
select * from stu