内置函数

select  abs(-100) from dual;

select  mod(22,3 ) from dual;

select ceil(12.0)from dual; select floor(12.5)from dual;

select round(12.445 ,2) from dual;   --截取 select trunc(12.345,2)from dual;

select xingm, length(xingm)from t_hq_ryxx;

--截取字符串

select xingm, substr(xingm,1,2 )from t_hq_ryxx;

select xingm, substr(xingm,-2,2 )from t_hq_ryxx; select xingm, substr(xingm,-3,1 )from t_hq_ryxx;

--字符串连接

select concat('dasd','dsada' )from dual;

select concat('dasd' ,concat('sadas', 'dsada') )from dual;

select 'sdas'||'sadas'||'sdas' from dual;

select instr('abdcdefdg','d')from dual;

--从第三个开始找

select instr('adbcdefgd','d',3)from dual;

select instr('abdcdefdg','dd')from dual;

select upper ('asdrgcvb'), lower('SHJASDKJ'),initcap('wo cao ni mei') from dual;

select replace ('sdjsadhkja','sa','123') from dual;

--更新替换

update  T_HQ_RYXX t set xingm = replace(xingm,'李','赵')  where xingm like '李%';

--填充

select rpad('aa',8,'c')from dual;

select rpad('aa',8)from dual;

select lpad('aa',8,'c')from dual;

--去空格

select trim ('  dasdas   ') from dual;

select ltrim ('  dasdas   ') from dual;

select rtrim ('  dasdas   ') from dual;

select trim (leading'a' from 'aasdsd') from dual;

select trim (trailing'a' from 'aasdsda') from dual;

select trim (both'a' from 'aasdsda') from dual;

--当前时间

select sysdate from dual;

--月份加减

select add_months(sysdate,2) from dual;

select add_months(sysdate,-2) from dual;

select last_day(sysdate) from dual;

select last_day(sysdate)+ 10 from dual;

select cast('123' as number) +123 from dual;

select cast(12345 as varchar2(5)) from dual; select cast(12345 as varchar2(5))+ 123 from dual;

select cast (sysdate as varchar2(20)) from dual;

--日期转换

select to_char(sysdate,'YYYY-DD-MM') from dual

select to_char(sysdate,'yy-mm-dd hh:mi:ss') from dual

select to_char(sysdate,'yy-mm-dd hh24:mi:ss') from dual

select to_char(123.456,'9999.9') from dual;

select  to_date('2015-11-11 12:33:45','yyyy-mm-dd hh24:mi:ss')from dual;

update t_hq_ryxx set ruzrq = to_date('2015-12-31','yyyy-mm-dd')where bianh = '104';

select t.*, t.rowid from T_HQ_RYXX t where ruzrq > to_date('2015-10-11','yyyy-mm-dd');

select to_number ('123.456' ,'99999.99999')from dual;

--年龄为空的替换为20

select nvl(nianl,20) from t_Hq_Ryxx;

select  nvl(nianl,0) + gongz from t_Hq_Ryxx;

--不为空替换为20，为空替换为1000

select  nvl2(nianl,20,1000) + gongz from t_Hq_Ryxx;

--区查处结果的相反结果

select * from t_hq_ryxx where lnnvl(nianl > 20);