EXTRACT extracts and returns the value of a specified datetime field from a datetime or interval value expression.
The field you are extracting must be a field of the datetime_value_expr
or interval_value_expr
. For example, you can extract only YEAR
, MONTH
, and DAY
from a DATE
value. Likewise, you can extract TIMEZONE_HOUR
and TIMEZONE_MINUTE
only from the TIMESTAMP
WITH
TIME
ZONE
datatype.
eg.
YEAR
FROM SYSDATE) FROM DUAL; return Current Year MONTH
FROM SYSDATE) FROM DUAL; return Current Month DAY
FROM SYSDATE) FROM DUAL; return Current Day HOUR
FROM SYSDATE) FROM DUAL;Error HOUR
FROM TIMESTAMP '2005-10-10 10:10:10') FROM DUAL;
MINUTE
FROM SYSDATE) FROM DUAL;Error MINUTE
FROM TIMESTAMP '2005-10-10 10:10:10') FROM DUAL;
YEAR
FROM SYSDATE)中FROM 的下一个参数是日期类型的时候可以抽取年月日.就是说这个参数是日期类型的时候就可以抽取年\月\日,而抽取不了时\分部分.抽取时分部分得在FROM 后面加带TIMESTAMP 且后面加时间字符.MINUTE
FROM TIMESTAMP '2005-10-10 10:10:10')中,如果把'2005-10-10 10:10:10'用日期类型的字段来代替并转换成字符类型后,也是错误的,估计是这方法的问题.
比如(MINUTE
FROM TIMESTAMP to_date(to_char(日期类型,'YYYY-MM-DD hh24:mi:ss'),'YYYY-MM-DD hh24:mi:ss')),这样执行不了的.
如果真要从日期类型的字段中抽取时\分部分用to_char() 函数就可以了.比如to_char(日期类型,'hh24:mi')
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