trunc函数示例

1、时间处理

select trunc(sysdate) from dual  
--2011-3-18 今天的日期为2011-3-18

select trunc(sysdate, 'mm')   from   dual  
--2011-3-1 返回当月第一天.

select trunc(sysdate,'yy') from dual  
--2011-1-1 返回当年第一天

select trunc(sysdate,'dd') from dual  
--2011-3-18 返回当前年月日

select trunc(sysdate,'yyyy') from dual  
--2011-1-1 返回当年第一天

select trunc(sysdate,'d') from dual  
--2011-3-13 (星期天)返回当前星期的第一天

select trunc(sysdate, 'hh') from dual   
--2011-3-18 14:00:00 当前时间为14:41   

select trunc(sysdate, 'mi') from dual  
--2011-3-18 14:41:00 TRUNC()函数没有秒的精确

2、数字处理

select trunc(123.458) from dual 
--123

select trunc(123.458,0) from dual 
--123

select trunc(123.458,1) from dual 
--123.4

select trunc(123.458,-1) from dual 
--120

select trunc(123.458,-4) from dual 
--0

select trunc(123.458,4) from dual  
--123.458

select trunc(123) from dual  
--123

select trunc(123,1) from dual 
--123

select trunc(123,-1) from dual 
--120

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