postgresql 获取日期时间的方法

获取当前事务的日期和/或时间∶

CURRENT_DATE
CURRENT_TIME
CURRENT_TIME (precision)
CURRENT_TIMESTAMP
CURRENT_TIMESTAMP (precision)

LOCALTIME
LOCALTIME (precision)
LOCALTIMESTAMP
LOCALTIMESTAMP (precision)

now()
transaction_timestamp()

$ psql 
psql (9.1.24)
Type "help" for help.

postgres=# select now();
              now              
-------------------------------
 2018-07-25 11:15:26.238933+08
(1 row)

postgres=# begin;
BEGIN
postgres=# x
Expanded display is on.
postgres=# select current_date,
                  current_time,
                  current_time(6),
                  current_timestamp,
                  current_timestamp(6),
                  localtime,
                  localtime(6),
                  localtimestamp,
                  localtimestamp(6),
                  now(),
                  transaction_timestamp();
-[ RECORD 1 ]---------+------------------------------
date                  | 2018-07-25
timetz                | 11:15:33.138884+08
timetz                | 11:15:33.138884+08
now                   | 2018-07-25 11:15:33.138884+08
timestamptz           | 2018-07-25 11:15:33.138884+08
time                  | 11:15:33.138884
time                  | 11:15:33.138884
timestamp             | 2018-07-25 11:15:33.138884
timestamp             | 2018-07-25 11:15:33.138884
now                   | 2018-07-25 11:15:33.138884+08
transaction_timestamp | 2018-07-25 11:15:33.138884+08

获取当前实时时间

statement_timestamp()
clock_timestamp()
timeofday()

postgres=# select statement_timestamp(),clock_timestamp(),timeofday();
-[ RECORD 1 ]-------+------------------------------------
statement_timestamp | 2018-07-25 11:19:03.633837+08
clock_timestamp     | 2018-07-25 11:19:03.634195+08
timeofday           | Wed Jul 25 11:19:03.634203 2018 CST