NUMTODSINTERVAL

numtodsinterval(,)  x是一个数字、c是一个字符串，表明x的单位，这个函数把x转为interval day to second数据类型。

teledb=# select sysdate,sysdate+numtodsinterval(2,'hour') as res from dual; 
        orcl_sysdate        |            res         
----------------------------+----------------------------
 2023-08-24 10:49:53.417051 | 2023-08-24 12:49:53.417051
(1 row)

teledb=#

DBTIMEZONE

teledb=# select DBTIMEZONE from dual;
 dbtimezone 
------------
 08:00:00
(1 row)

teledb=# 

MONTHS_BETWEEN

teledb=# select months_between(to_date('20210331', 'yyyymmdd'), to_date('20200131', 'yyyymmdd')) as months from dual;
 months 
--------
     14
(1 row)

teledb=#

LAST_DAY

LAST_DAY函数返回指定日期对应月份的最后一天。

teledb=# SELECT last_day('2020-05-01') FROM dual;  
        last_day    
------------------------
 2020-05-31 00:00:00+08
(1 row)

teledb=#

ADD_MONTHS

ADD_MONTHS(x,y)

x值为日期，y值为数量，用于计算某个日期向前或者向后y个月后的时间。

teledb=# select add_months(sysdate,1) from dual;  
         add_months     
----------------------------
 2023-09-24 11:08:17.194487
(1 row)

teledb=# select add_months(sysdate,-1) from dual;
         add_months     
----------------------------
 2023-07-24 11:08:21.019573
(1 row)

teledb=#