postgresql根据已知的一个日期,查询数据库中这个日期所属的月份的所有...

发布网友 发布时间：2022-04-23 00:45

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懂视网 时间：2022-05-01 14:41

1.1 获取当前完整时间

select now();

david=# select now();
  now  
-------------------------------
 2013-04-12 15:39:40.399711+08
(1 row)

david=# 

current_timestamp 同 now() 函数等效。

david=# select current_timestamp;
  now  
-------------------------------
 2013-04-12 15:40:22.398709+08
(1 row)

david=# 

1.2 获取当前日期

select current_date;

david=# select current_date;
 date 
------------
 2013-04-12
(1 row)

david=# 

1.3 获取当前时间

select current_time;

david=# select current_time;
 timetz 
--------------------
 15:43:31.101726+08
(1 row)

david=#

二、时间的计算

david=# select now();
  now  
-------------------------------
 2013-04-12 15:47:13.244721+08
(1 row)

david=#

2.1 两年后

david=# select now() + interval ‘2 years‘;
  ?column?  
-------------------------------
 2015-04-12 15:49:03.168851+08
(1 row)

david=# select now() + interval ‘2 year‘; 
  ?column?  
-------------------------------
 2015-04-12 15:49:12.378727+08
(1 row)

david=# select now() + interval ‘2 y‘; 
  ?column?  
------------------------------
 2015-04-12 15:49:25.46986+08
(1 row)

david=# select now() + interval ‘2 Y‘;
  ?column?  
-------------------------------
 2015-04-12 15:49:28.410853+08
(1 row)

david=# select now() + interval ‘2Y‘; 
  ?column?  
-------------------------------
 2015-04-12 15:49:31.122831+08
(1 row)

david=# 

2.2 一个月后

david=# select now() + interval ‘1 month‘; 
  ?column?  
------------------------------
 2013-05-12 15:51:22.24373+08
(1 row)

david=# select now() + interval ‘one month‘;
ERROR: invalid input syntax for type interval: "one month"
LINE 1: select now() + interval ‘one month‘;
    ^
david=# 

2.3 三周前

david=# select now() - interval ‘3 week‘;
  ?column?  
-------------------------------
 2013-03-22 16:00:04.203735+08
(1 row)

david=# 

2.4 十分钟后

david=# select now() + ‘10 min‘;   
  ?column?  
-------------------------------
 2013-04-12 16:12:47.445744+08
(1 row)

david=# 

说明：

interval 可以不写，其值可以是：

2.5 计算两个时间差

使用 age(timestamp, timestamp)

david=# select age(now(), timestamp ‘19-02-05‘);
   age   
----------------------------------------
 24 years 2 mons 7 days 17:05:49.119848
(1 row)

david=# 

david=# select age(timestamp ‘2007-09-15‘); 
  age  
------------------------
 5 years 6 mons 27 days
(1 row)

david=#

三、时间字段的截取

在开发过程中，经常要取日期的年，月，日，小时等值，PostgreSQL 提供一个非常便利的EXTRACT函数。

EXTRACT(field FROM source)

field 表示取的时间对象，source 表示取的日期来源，类型为 timestamp、time 或 interval。

3.1 取年份

david=# select extract(year from now());
 date_part 
-----------
 2013
(1 row)

david=# 

3.2 取月份

david=# select extract(month from now()); 
 date_part 
-----------
  4
(1 row)

david=# 

david=# select extract(day from timestamp ‘2013-04-13‘);
 date_part 
-----------
 13
(1 row)

david=# 

david=# SELECT EXTRACT(DAY FROM INTERVAL ‘40 days 1 minute‘);
 date_part 
-----------
 40
(1 row)

david=# 

3.3 查看今天是一年中的第几天

david=# select extract(doy from now());
 date_part 
-----------
 102
(1 row)

david=# 

3.4 查看现在距1970-01-01 00:00:00 UTC 的秒数

david=# select extract(epoch from now());
 date_part 
------------------
 1365755907.94474
(1 row)

david=# 

3.5 把epoch 值转换回时间戳

david=# SELECT TIMESTAMP WITH TIME ZONE ‘epoch‘ + 1369755555 * INTERVAL ‘1 second‘; 
 ?column? 
------------------------
 2013-05-28 23:39:15+08
(1 row)

david=# 

以上是基本的PG时间/日期函数使用，可满足一般的开发运维应用。

3.6 求取两个timestamp之间的月份差

select 
EXTRACT(YEAR from age(‘2016-09-19 00:00:00.000000‘, ‘2012-12-31 00:00:00.000000‘))*12+ 
EXTRACT(MONTH from age(‘2016-09-19 00:00:00.000000‘, ‘2012-12-31 00:00:00.000000‘))

详细用法请参考：

PostgreSQL官方说明：http://www.postgresql.org/docs/9.2/static/functions-datetime.html

PostgreSQL的时间/日期函数使用

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热心网友 时间：2022-05-01 11:49

david=# select extract(year from now());
date_part
-----------
2013
(1 row)
david=# 3.2 取月份

david=# select extract(month from now());
date_part
-----------
4
(1 row)
david=#
david=# select extract(day from timestamp '2013-04-13');
date_part
-----------
13
(1 row)
david=#
david=# SELECT EXTRACT(DAY FROM INTERVAL '40 days 1 minute');
date_part
-----------
40
(1 row)
david=# 3.3 查看今天是一年中的第几天

david=# select extract(doy from now());
date_part
-----------
102
(1 row)
david=# 3.4
查看现在距1970-01-01 00:00:00 UTC 的秒数

david=# select extract(epoch from now());
date_part
------------------
1365755907.94474
(1 row)
david=# 3.5 把epoch 值转换回时间戳

david=# SELECT TIMESTAMP WITH TIME ZONE 'epoch' + 1369755555 * INTERVAL '1 second';
?column?
------------------------
2013-05-28 23:39:15+08
(1 row)
david=#

--取day
skytf=> select extract(day from now());
date_part
-----------
3
(1 row)
skytf=> select extract(day from timestamp '2011-06-03');
date_part
-----------
3
(1 row)
skytf=> select timestamp '2011-06-03';
timestamp
---------------------
2011-06-03 00:00:00
(1 row)

--取小时
skytf=> select extract (hour from now());
date_part
-----------
14
(1 row)

--取分钟
skytf=> select extract (minute from now());
date_part追问内容丰富 ， 找不到重点