Oracle日付関数&計算日の使用

SELECT MONTHS_BETWEEN('2021/07/07', '2021-05-08')  

FROM dual; / 결과값 : 1.99697057945041816009557945041816009558

SELECT ADD_MONTHS('2021/07/07', 2)  

from dual;  /  결과값 : 2021/09/07

SELECT LAST_DAY('2021/07/07')  

from dual;  / 결과값 : 2021/07/31

SELECT NEXT_DAY('2021/07/07', '수요일')  

from dual;   / 결과값 : 2021/07/14 

select to_date('2021/07/07') + 10  

from dual;  / 결과값 : 2021/07/17

select to_date('2021-02-25','YYYY-MM-DD') - to_date('2021-02-21','YYYY-MM-DD')  

from dual;  / 결과값 : 4

[날짜 포맷 설정]

alter session set nls_date_format ='yyyy/mm/dd /hh24:mi:ss';

alter session set nls_date_format ='yyyy/mm/dd';

SELECT SYSDATE  
    , SYSDATE + 1/24  
    , SYSDATE + 5/(24*60)  
    , SYSDATE + 10/(24*60*60)  

FROM dual ;

select to_date('2021-07-07') +  6/24+23/(24*60)+43/(24*60*60)

from dual;  결과값 : 2021/07/07 06:23:43