ORACLE date plus minus function __ function

Add_months: Add Month
SELECT Sysdate,add_month (sysdate,1) from DUAL;
Sysdate add_months (sysdate,1)
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03-1-8 16:2 03-2-8 16:21:59

Plus Day:sql> SELECT sysdate,sysdate+1 from DUAL;

Sysdate sysdate+1
-----------   -----------
03-1-8 16:2 03-1-9 16:2

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No addition between date and date

Sql> select Sysdate+sysdate from dual;

Select Sysdate+sysdate from dual

ORA-00975: Date + date not allowed

Date and number can be added

Sql> select sysdate+1 from dual;

Sysdate+1
-----------
2003-1-9 16:52:32

Date and date can be subtracted

Sql> select Sysdate-sysdate from dual;

Sysdate-sysdate
---------------
0

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Add_months (d,x)
Return d date plus x month date
Last_day (D)
Returns the date of the last day of the month that contains the date D

Add_months (sysdate,1) plus one months

Add_months (sysdate,-1) minus one months

Sysdate+1 Plus One day

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Months_between (D1,D2)
Returns the number of months between D1, D2

New_time (D,Z1,Z2)
Returns the time zone Z1 Z2 time

Next_day (D,s)
Returns the next day that satisfies the condition s
s for the day of the week

Round (D,F)
Date d is rounded by format F

Sysdate
Returns the current time of the database

Trunc (D,F)
In format f truncate time D

In addition: the date can be directly added minus
such as: Sysdate +1,sysdate-1

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Sysdate+1 plus one day
sysdate+1/24 plus 1 hours
sysdate+1/(24*60) plus 1 minutes
sysdate+1/(24*60*60) plus 1 seconds
analogy to milliseconds 0.001 sec