oracle中trunc()和to_char()函数用法

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oracle中trunc()和to_char()函数⽤法

-----trunc(for date)

select sysdate from dual; --当前时间 2016/9/7 10:32:04

select trunc(sysdate) from dual;--取当天 2016/9/7

select trunc(sysdate,'yyyy') from dual; --取当年第⼀天 2016/1/1

select trunc(sysdate,'mm') from dual; --取当⽉第⼀天 2016/9/1

select trunc(sysdate,'dd') from dual; --取当天 2016/9/7

select trunc(sysdate,'d') from dual; --返回当前星期的第⼀天 2016/9/4

select trunc(sysdate,'hh') from dual; --返回当前时间,精确到⼩时 2016/9/7 10:00:00

select trunc(sysdate,'mi') from dual; --返回当前时间,精确到分钟 2016/9/7 10:32:00

--trunc(for number)

select trunc(2016.11) from dual; --2016

select trunc(2016.99) from dual; --2016

select trunc(2016.99,1) from dual; --2016.9

select trunc(2016.99,3) from dual; --2016.99

select trunc(2016.99,-1) from dual; --2010

select trunc(2016.99,-2) from dual; --2000

select trunc(2016.99,-4) from dual; --0

select trunc(2016,1) from dual; --2016

select trunc(2016,-1) from dual; --2010

select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') as nowTime from dual; --⽇期转化为字符串 2016-09-07 10:33:11

select to_char(sysdate,'yyyy') as nowYear from dual; --获取时间的年 2016

select to_char(sysdate,'mm') as nowMonth from dual; --获取时间的⽉ 09

select to_char(sysdate,'dd') as nowDay from dual; --获取时间的⽇ 07

select to_char(sysdate,'hh24') as nowHour from dual; --获取时间的时 10

select to_char(sysdate,'mi') as nowMinute from dual; --获取时间的分 33

select to_char(sysdate,'ss') as nowSecond from dual; --获取时间的秒 11

select to_char(sysdate,'day') as nowDay from dual; --获取当天是星期⼏ 星期三

select to_char(sysdate,'D') as nowDay from dual; --获取当天是星期⼏ 4

select floor(sysdate - to_date('2016-08-05','yyyy-mm-dd')) from dual; --取两个⽇期间的天数 33