Postgresql日付と時間タイプ

timestamp with[out] time zone        (  )  
time with[out] time zone   		          (  )    

       。MySQL    。
         ，       with time zone。

highgo=# select time '120900';
   time   
----------
 12:09:00
(1 row)

highgo=# select time '120900 PST';
   time   
----------
 12:09:00
(1 row)

highgo=# select time WITH time zone '120900 PST';
   timetz    
-------------
 12:09:00-08
(1 row)



      ，      。       datestyle。

highgo=# create table t(date date);
CREATE TABLE
highgo=# insert into t values (date '12-18-2010');
INSERT 0 1
highgo=# select * from t;
    date    
------------
 2010-12-18
(1 row)

highgo=# show datestyle;
 DateStyle 
-----------
 ISO, MDY
(1 row)

highgo=# set datestyle = 'YMD';
SET

highgo=# insert into t values (date '2010-12-19');
INSERT 0 1
highgo=# select * from t;
    date    
------------
 2010-12-18
 2010-12-19
(2 rows)


 ：      2017-12-18         。       2017 12 18 。

PostgreSQL                  。
                   ：
CURRENT_DATE
CURRENT_TIME
CURRENT_TIMESTAMP
CURRENT_TIME(precision)
LOCALTIME
LOCALTIMESTAMP
now()
transaction_timestamp()               

             ，           。
statement_timestamp()
clock_timestamp()
timeofday()                  text   


       ， now()          ， statement_timestamp()         。

highgo=# begin;
BEGIN
highgo=# select now();
              now              
-------------------------------
 2017-12-18 12:18:32.263891+08
(1 row)

highgo=# select now();
              now              
-------------------------------
 2017-12-18 12:18:32.263891+08
(1 row)

highgo=# select statement_timestamp();
      statement_timestamp      
-------------------------------
 2017-12-18 12:19:15.463267+08
(1 row)

highgo=# select statement_timestamp();
      statement_timestamp      
-------------------------------
 2017-12-18 12:19:18.975693+08
(1 row)

highgo=# commit;
COMMIT

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