Oracle简单的函数

--大小写函数

select lower('YZW')from dual

select upper('yzw')from dual
--帕斯卡
select initcap('yzw six six six') from dual
--substr
select substr('YZW666',1,2) from dual

--3.求字符个数
select length('YZW666') from dual
--字节个数
select lengthb('叶') from dual

--求出小字符串在大字符串中出现的位置
select instr('YZW666','Z') from dual

--参数
select instr('AORBORCORDOREOR','OR',-3,2) from dual

--lpad()
select lpad('Happy',10,'☆') from dual
select rpad('Happy',10,'☆') from dual

--trim()
select trim(' A BC ') from dual

select trim('a' from 'a BCa') from dual

--日期函数
months_between 两个日期相差的月数
select months_between(sysdate,to_date('1999-05-05','yyyy-mm-dd')) from dual;
--日期相减
--按天数
select floor(sysdate-to_date('05-05-1999','MM-DD-YYYY')) from dual
select floor(sysdate-to_date('1999-05-05','yyyy-mm-dd')) from dual
--显示转换
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual

select to_number('12.23') from dual

select '12.23'+'23.34' from dual

select to_char(sal,'L999,999.9') from emp

select * from emp

--数字函数
select round(12.55,0) from dual

select trunc(12.99,1) from dual

--滤空函数
select ename,sal+nvl(comm,0) as 薪资 from emp;

select ename,sal+nvl2(comm,comm*2,0) as 薪资 from emp

--decode函数
select ename,decode(deptno,10,'开发部',20,'测试部',30,'财务部',40,'保洁部','人事部') as 部门 from emp