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select t.*, b.bummc from t_hq_ryxx t,t_hq_bm b where t.bum = b.bumbm;

select * from t_hq_ryxx t full join t_hq_bm b on t.bum > b.bumbm;

select * from t_hq_ryxx a, t_hq_ryxx b where a.bum = b.bum and a.xingb = '1';

select to_number('123.456','999.999') from dual;

select abs(-100) from dual;--绝对值

select mod(9,3) from dual;--求余数

select ceil(11.5) from dual;--上限值

select floor(12.5) from dual;--下限值

select round(12.456,2) from dual;--四舍五入

select trunc(12.456,2) from dual;--截取

select xingm, length(xingm) from t_hq_ryxx; 

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

select concat('aas',concat('sadas','aasw')) from dual;

select 'as' || 'eew' || 'weq' from dual;

select instr('adsdfdsfdfg','d',3) from dual;--查找字符串

select upper('assdsad'),lower('ASFFA'), initcap('are you bitch?') from dual;

select replace('asfafasd','fa','22') from dual;--查找替换

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

select lpad('sa',8,'cd') from dual;

select trim('  sadfs  ') from dual;--去空格

select ltrim('   adad  ') from dual;

select rtrim('   adad  ') from dual;

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

select sysdate from dual;

select add_months(sysdate,-20) from dual;

select last_day(sysdate) + 12 from dual;

select cast('123'as number) + 312 from dual;--转换

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

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

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

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

select to_date('2015-12-21 12:31:33','yyyy-mm-dd hh24:mi:ss') +1 from dual;

select nvl2(nianl,20,1000) from t_hq_ryxx;

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