2019独角兽企业重金招聘Python工程师标准>>> 
date
postgres=# select date'2015-2-28',date'2015-2-28 12:22:30';
date | date
------------+------------
2015-02-28 | 2015-02-28
(1 row)
日期只有年月日
time
postgres=# select time '000001.111',time'24:00:00',time '2013-11-11 11:23:44';
time | time | time
--------------+----------+----------
00:00:01.111 | 24:00:00 | 11:23:44
(1 row)
时间有时分秒毫秒,可以出现24:00:00.
timestamp
postgres=# select timestamp '2015-2-28 12:11:22.123411',timestamp with time zone '2015-2-28 24:00:00';
timestamp | timestamptz
----------------------------+------------------------
2015-02-28 12:11:22.123411 | 2015-03-01 00:00:00+08
(1 row)
timestamp中的24点变成第二天的0点
特殊关键字
epoch
postgres=# select date 'epoch',timestamp 'epoch';
1970-01-01 | 1970-01-01 00:00:00
特定时间戳
infinity
postgres=# select date 'infinity',timestamp '-infinity';
infinity | -infinity
正负无穷大
now
postgres=# select date 'now',timestamp 'now',time 'now';
2015-02-28 | 2015-02-28 23:16:27.991058 | 23:16:27.991058
tomorrow,today,yesterday
postgres=# select date'tomorrow',date 'today',date'yesterday';
2015-03-01 | 2015-02-28 | 2015-02-27
postgres=# select timestamp'tomorrow',timestamp'today',timestamp'yesterday';
2015-03-01 00:00:00 | 2015-02-28 00:00:00 | 2015-02-27 00:00:00
昨天今天明天,时分秒都是0
但是你也可以这样写:
postgres=# select timestamp 'yesterday 11:00:00',timestamp 'today 12:';
2015-02-14 11:00:00 | 2015-02-15 12:00:00
allballs
postgres=# select time'allballs';
00:00:00
只适用time类型
interval
postgres=# select interval '1-2 3 4:5:6.777777',interval '1 year 3 hour 87 second';
1 year 2 mons 3 days 04:05:06.777777 | 1 year 03:01:27
postgres=# select interval 'P1Y2M3DT4H5M6S',interval 'P1-2-3T4:5:6.7';
1 year 2 mons 3 days 04:05:06 | 1 year 2 mons 3 days 04:05:06.7
影响时间输出的格式
datestyle
时间相关的显示格式
postgres=# show datestyle;
ISO, MDY
postgres=# select now();
2015-02-28 23:42:39.748022+08
postgres=# set datestyle='postgres,dmy';
SET
postgres=# select now();
Sat 28 Feb 23:42:12.606023 2015 CST
postgres=# reset datestyle;
RESET
intervalstyle
interval显示的格式
postgres=# show intervalstyle;
postgres
postgres=# select interval '1-2 3 4:5:6.777777';
1 year 2 mons 3 days 04:05:06.777777
postgres=# set intervalstyle=sql_standard;
SET
postgres=# select interval '1-2 3 4:5:6.777777';
+1-2 +3 +4:05:06.777777
postgres=# set intervalstyle=postgres_verbose;
SET
postgres=# select interval '1-2 3 4:5:6.777777';
@ 1 year 2 mons 3 days 4 hours 5 mins 6.777777 secs
postgres=# set intervalstyle=iso_8601;
SET
postgres=# select interval '1-2 3 4:5:6.777777';
P1Y2M3DT4H5M6.777777S
postgres=# reset intervalstyle;
RESET
跟输入格式相对应