select abs (-) from dual;--绝对值
select mod (,) from dual;--取模,取余数
select ceil (12.1) from dual;--去上限值
select floor (12.1) from dual;--去下限值
select round (12.4567,) from dual; -- 四舍五入
select trunc (12.456,) from dual; -- 截取，不四舍五入
select trunc (12.456,) from dual; -- 截取，不四舍五入(截整)
select length ('asddsa') from dual;--字符串长度
select xingm, length (xingm) from t_hq_ryxx;
select xingm, substr (xingm,,) from t_hq_ryxx;--截取，（从第一位开始截取，截两位）
select concat ('sa',concat ('sdsd','ddd')) from dual;
select 'sa'||'sdsd'||'ddd' from dual;
--查找字符串
select instr ('abcdef','d') from dual;
select instr ('abcdefdf','d',) from dual;
select instr ('abcdefdf','d',) from dual; --数字指定起始位置
select instr ('abcdefdf','dd',) from dual; --找不到返回0
--转换大小写
select upper ('assa'),lower ('SDDA') from dual;
select upper ('assa'),lower ('SDDA'), initcap ('this is a car') from dual; --initcap 首字母转换大写
select replace ('abcdef','ab','') from dual; --替换
update t_hq_ryxx set xingm = replace (xingm,'三','四') where xingm like '三%'
--填充
select rpad ('aa',, 'c') from dual;
select rpad ('aba',, 'de') from dual;
select lpad ('aa',, 'rc') from dual;
--去空格
select trim (' wfat ') from dual; --去前后空格
select ltrim (' sd1 ') from dual; --去左空格
select rtrim (' sdad ') from dual; --去右空格
--去前缀
select trim (leading 'a' from 'asda') from dual; --前边开始
select trim (trailing 'a' from 'asda') from dual; --右边开始
select trim (both 'a' from 'asda') from dual; --去前后
--日期型函数
select sysdate from dual;
select add_months(sysdate,) from dual; --加两个月
select add_months(sysdate,-) from dual; --减两个月
select last_day(sysdate) from dual;
select last_day(sysdate) + from dual; --（+）加天数
select last_day(sysdate) - from dual; --（-）减天数
--转换函数
--select cast ('' as number) from dual;
--select cast ('' as number) + from dual;
--select cast ('' as varchar2()) from dual; --数字长度不能超过字符串长度
--select cast(sysdate as varchar2()) from dual;
select to_char(sysdate, 'YYYY-MM-DD')from dual; --日期转换字符串(忽略大小写)
select to_char(sysdate, 'yy-mm-dd')from dual;
select to_char(sysdate, 'YYYY-DD-MM HH24:mi:ss')from dual;
--select to_char(123.456,'9999.9')from dual;
select to_date('2015-12-11','yyyy-mm-dd') from dual; --字符串转换日期
select to_number('123.456','9999.999') from dual;
select( nianl + gongz) from t_hq_ryxx;
