oracle 一些常用的函数

select * from emp where empno=7839;

select sal from emp where empno=7839;

字符函数

select length(sal) from emp;

select lower(ename) from emp;

select upper(ename) from emp;

select substr(sal,1,3) from emp;

select replace(sal,'a','dddddddddddd') from emp;

select round(sal,1) from emp where empno=7839;

select comm from emp where empno=7839;

select trunc(comm) from emp where empno=7839;

select trunc(comm,1) from emp where empno=7839;

select ceil(comm) from emp wher+e empno=7839; ---向上取整

select floor(comm) from emp where empno=7839; --向下取整

select mod(10,3) from dual;

select floor(sal) from emp;

select sysdate from dual;

select * from emp where sysdate> add_months(hiredate,8*12); --- 工龄超过8年的

select trunc(sysdate-hiredate),ename from emp;

select hiredate,last_day(hiredate) from emp;

select hiredate ,ename from emp where last_day(hiredate)-2=hiredate; ---某个月的倒数第三天

select to_char(hiredate,'yyyy-MM-dd hh:mi:ss') from emp;

select to_char(hiredate,'yyyy-MM-dd hh24:mi:ss') from emp;

insert into emp values(8881,'testUser','manager',7782,sysdate,100,1000,10);

insert into emp values(8882,'testUser','manager',7782,to_date('2012-12-20 23:12:12','yyyy-MM-dd hh24:mi:ss'),100,1000,10);

commit;

select * from emp where empno=8882;

select to_char(sal,'L9,999.99') from emp;

select to_char(sal,'$9,999.99') from emp;

select ename,hiredate from emp where to_char(hiredate,'MM')=12; --查询12月入职的员工

select ename,hiredate from emp where to_char(hiredate,'yyyy')=1980; --查询1980 入职的员工

系统函数

select sys_context('USERENV','db_name') from dual;

select sys_context('USERENV','current_schema') from dual;

select sys_context('USERENV','language') from dual;

select sys_context('USERENV','session_user') from dual;

--只读存储过程是用来获得，某个时间的数据

set transaction read only;

用户和方案的关系

一个用户对应一个方案，用户以方案的方式管理 数据库对象

一个方案包括 表 视图 触发器 存储过程