greenplum⽇期及时间函数1.⽇期和时间间字段
date:⽇期字段，格式:2016-04-15
timestamp：时间字段，格式:2016-04-15 20:00:00
2.获取当时时间函数
postgres=# select now();
now
-------------------------------
2016-05-03 17:06:16.334648+08
postgres=# select current_timestamp;
now
-------------------------------
2016-05-03 17:12:30.403614+08
postgres=# select CURRENT_TIME;
timetz
------------------
17:21:20.1946+08
postgres=# select LOCALTIME;
time
-----------------
17:22:15.856583
postgres=# select LOCALTIMESTAMP;
timestamp
-
---------------------------
2016-05-03 17:22:27.235583
3.获取当天⽇期
postgres=# select current_date;
date
------------
2016-05-03
4.⽇期计算：
--使⽤interval
postgres=# select now()+interval '2 day';
column
-
------------------------------
2016-05-05 17:26:07.931652+08
postgres=# select now()-interval '2 day';
column
-------------------------------
2016-05-01 17:26:43.908585+08
postgres=# select now()+interval '2 hour';
column
-------------------------------
2016-05-03 19:26:52.005566+08
5.时间截取
postgres=# select extract(year from now());
date_part
-----------
2016
postgres=# select extract(mon from now());
date_part
-----------
5
6.时间转换
postgres=# select timestamp '2012-05-12 18:54:54';
timestamp
-
--------------------
2012-05-12 18:54:54
postgres=# select date '2012-05-12 18:54:54';
date
------------
2012-05-12
postgres=# select date '2012-05-12 18:54:54';
dateunix时间戳转换日期格式
------------
2012-05-12
postgres=# select TIMESTAMP WITH TIME ZONE '2012-05-12 18:54:54' ;
timestamptz
------------------------
2012-05-12 18:54:54+08
7.与unix时间戳的转换

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