• //oracle中extract()函數從oracle?9i中引入,用于從一個date或者interval類型中截取到特定的部分??
• //語法如下：??
• EXTRACT?(??
• ????????{?YEAR?|?MONTH?|?DAY?|?HOUR?|?MINUTE?|?SECOND?}??
• ????????|?{?TIMEZONE_HOUR?|?TIMEZONE_MINUTE?}??
• ????????|?{?TIMEZONE_REGION?|?TIMEZONE_ABBR?}??
• FROM?{?date_value?|?interval_value?}?)??
• //我們只可以從一個date類型中截取?year,month,day(date日期的格式為yyyy-mm-dd);??
• //我們只可以從一個?timestamp?with?time?zone?的數據類型中截取TIMEZONE_HOUR和TIMEZONE_MINUTE;??
• select?extract(year?from?date'2011-05-17')?year?from?dual;??
• ??????YEAR??
• ----------??
• ??????2011??
• select?extract(month?from?date'2011-05-17')?month?from?dual;??
• ?????MONTH??
• ----------??
• ?????????5??
• select?extract(day?from?date'2011-05-17')?day?from?dual;??
• ???????DAY??
• ----------??
• ????????17??
• //獲取兩個日期之間的具體時間間隔，extract函數是最好的選擇??
• select?extract(day?from?dt2-dt1)?day??
• ??????,extract(hour?from?dt2-dt1)?hour??
• ??????,extract(minute?from?dt2-dt1)?minute??
• ??????,extract(second?from?dt2-dt1)?second??
• from?(??
• ?????select?to_timestamp('2011-02-04?15:07:00','yyyy-mm-dd?hh24:mi:ss')?dt1??
• ???????????,to_timestamp('2011-05-17?19:08:46','yyyy-mm-dd?hh24:mi:ss')?dt2??
• ?????from?dual)??
• /??
• ???????DAY???????HOUR?????MINUTE?????SECOND??
• ----------?----------?----------?----------??
• ???????102??????????4??????????1?????????46??
• --??
• select?extract(year?from?systimestamp)?year??
• ??????,extract(month?from?systimestamp)?month??
• ??????,extract(day?from?systimestamp)?day??
• ??????,extract(minute?from?systimestamp)?minute??
• ??????,extract(second?from?systimestamp)?second??
• ??????,extract(timezone_hour?from?systimestamp)?th??
• ??????,extract(timezone_minute?from?systimestamp)?tm??
• ??????,extract(timezone_region?from?systimestamp)?tr??
• ??????,extract(timezone_abbr?from?systimestamp)?ta??
• from?dual??
• /??
• ?????YEAR??????MONTH????????DAY?????MINUTE?????SECOND?????????TH?????????TM?TR?????????TA??
• ----------?----------?----------?----------?----------?----------?----------?---------?----------??
• ??????2011??????????5?????????17??????????7?????14.843??????????8??????????0?UNKNOWN???UNK?

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