Oracle日期計算之INTERVAL

在計算月份的時候除了add_months，還可用INTERVAL：

1.Connected to Oracle Database 11g Enterprise Edition Release 11.1.0.7.0  
2.Connected as xxpo  3.  
4.SQL>  
5.SQL> SELECT to_char(SYSDATE,'YYYY/MM/DD HH24:MI:SS') now FROM dual;  6.  
7.NOW 
8.------------------- 
9.2011/05/20 06:22:00 
10.SQL> SELECT to_char(add_months(SYSDATE,-1),'YYYY/MM/DD HH24:MI:SS') "1 month before" FROM dual;  11.  
12.1 month before 
13.------------------- 
14.2011/04/20 06:22:02 
15.SQL> SELECT to_char(SYSDATE + INTERVAL '-1' MONTH,'YYYY/MM/DD HH24:MI:SS') "1 month before" FROM dual;  16.  
17.1 month before 
18.------------------- 
19.2011/04/20 06:22:04 
20.SQL> SELECT to_char(SYSDATE + INTERVAL '1-1' YEAR TO MONTH,'YYYY/MM/DD HH24:MI:SS') "1 year and 1 month later" FROM dual;  21.  
22.1 year and 1 month later 
23.------------------------ 
24.2012/06/20 06:22:06 
25.SQL> SELECT to_char(SYSDATE + INTERVAL '-1-1' YEAR TO MONTH,'YYYY/MM/DD HH24:MI:SS') "1 year and 1 month before" FROM dual;  26.  
27.1 year and 1 month before 
28.------------------------- 
29.2010/04/20 06:22:08 
30.  
31.SQL>  
 

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