oracle获取日期的数字格式

select ryrq, extract (year from ryrq), extract (month from ryrq), extract (day from ryrq) from zy_brry where zyh=6830

上面的方法获取的都是把0省略后的值，目标是获取2016、04、02 

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select csny,substr(to_char(csny,'yyyy'),1,4) csyear,substr(to_char(csny,'mm'),1,2) csmonth，
substr(to_char(csny,'dd'),1,2) csday from zy_brry where zyh=6830

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上面这种方法截取一下也可以，

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这个substr截取日期好像规则与截取字符窜有点区别

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select substr(to_char(ryrq,'yyyy'),1,4) ryyear,substr(to_char(ryrq,'mm'),1,2) rymonth，
substr(to_char(ryrq,'dd'),1,2) ryday，substr(to_char(ryrq,'hh'),1,2) ryhour ,
substr(to_char(cyrq,'yyyy'),1,4) cyyear,substr(to_char(cyrq,'mm'),1,2) cymonth，
substr(to_char(cyrq,'dd'),1,2) cyday，substr(to_char(cyrq,'hh'),1,2) cyhour ,
substr(to_char(csny,'yyyy'),1,4) csyear,substr(to_char(csny,'mm'),1,2) csmonth，
substr(to_char(csny,'dd'),1,2) csday
from zy_brry where zyh=43439