id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	due_date
19	pg 中关于日期类型的计算问题	lisiliang	lslaing	"oracle 中关于时间类型的计算是相当的简单的，
oracle 对时间类型的计算 对运算符进行的重载。

pg 里的时间的计算比oracle 要弱不少，目前只实现了 date 类型的 “+” 操作

例如:
1	cyp_nw_app=> select current_date +7 ,current_date ;
2	  ?column?  |    date   
3	------------+------------
4	 2012-04-27 | 2012-04-20


对于time ，timestamp 类型的加减操作，操作的因子是要 interval 类型的数据的
例如：
01	cyp_nw_app=>   select interval '7days' ;
02	 interval
03	----------
04	 7 days
05	 
06	 
07	cyp_nw_app=> select current_timestamp , current_timestamp + interval '7d';
08	              now              |           ?column?           
09	-------------------------------+-------------------------------
10	 2012-04-20 15:07:31.425797+08 | 2012-04-27 15:07:31.425797+08
11	(1 DD？？？？)
12	 
13	cyp_nw_app=> select current_timestamp , current_timestamp + interval '7Y';
14	              now              |           ?column?           
15	-------------------------------+-------------------------------
16	 2012-04-20 15:07:37.165961+08 | 2019-04-20 15:07:37.165961+08
17	(1 DD？？？？)
18	 
19	cyp_nw_app=> select current_timestamp , current_timestamp + interval '7m';
20	              now              |           ?column?           
21	-------------------------------+-------------------------------
22	 2012-04-20 15:07:46.186136+08 | 2012-04-20 15:14:46.186136+08
23	(1 DD？？？？)
24	 
25	cyp_nw_app=> select current_timestamp , current_timestamp + interval '7w';
26	              now              |           ?column?           
27	-------------------------------+-------------------------------
28	 2012-04-20 15:07:52.080267+08 | 2012-06-08 15:07:52.080267+08
29	(1 DD？？？？)
30	 
31	cyp_nw_app=> select current_timestamp , current_timestamp + interval '7s';
32	              now              |           ?column?           
33	-------------------------------+-------------------------------
34	 2012-04-20 15:07:56.222229+08 | 2012-04-20 15:08:03.222229+08
35	(1 DD？？？？)
36	 
37	cyp_nw_app=> select current_timestamp , current_timestamp + interval '7h';
38	              now              |           ?column?           
39	-------------------------------+-------------------------------
40	 2012-04-20 15:08:04.816308+08 | 2012-04-20 22:08:04.816308+08
41	(1 DD？？？？)"	task 任务	closed	major	PG 测试计划进程	component1		fixed			20/04/2012