Oracle Database 提取日期的年，月，日，小时，分钟或秒部分
示例
DATE数据类型的年，月或日组成部分可以使用EXTRACT([YEAR|MONTH|DAY]FROMdatevalue)
SELECT EXTRACT (YEAR FROM DATE '2016-07-25') AS YEAR,
EXTRACT (MONTH FROM DATE '2016-07-25') AS MONTH,
EXTRACT (DAY FROM DATE '2016-07-25') AS DAY
FROM DUAL;输出：
YEAR MONTH DAY ---- ----- --- 2016 7 25
时间（小时，分钟或秒）部分可以通过以下任一方式找到：
使用CAST(datevalueASTIMESTAMP)将转换DATE为aTIMESTAMP，然后使用EXTRACT([HOUR|MINUTE|SECOND]FROMtimestampvalue);要么
使用TO_CHAR(datevalue,format_model)来获取值作为一个字符串。
例如：
SELECT EXTRACT( HOUR FROM CAST( datetime AS TIMESTAMP ) ) AS Hours,
EXTRACT( MINUTE FROM CAST( datetime AS TIMESTAMP ) ) AS Minutes,
EXTRACT( SECOND FROM CAST( datetime AS TIMESTAMP ) ) AS Seconds
FROM (
SELECT TO_DATE( '2016-01-01 09:42:01', 'YYYY-MM-DD HH24:MI:SS' ) AS datetime FROM DUAL
);输出：
HOURS MINUTES SECONDS
----- ------- -------
9 42 1