什么是 PostgreSQL 相当于 Oracle 的 SYSDATE？
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What is PostgreSQL equivalent of SYSDATE from Oracle?
提问by user2365917
I want to perform a query using sysdate like:
我想使用 sysdate 执行查询，例如：
select up_time from exam where up_time like sysdate
which is possible in Oracle.
这在 Oracle 中是可能的。
However, it seems that PostgreSQL doesn't support sysdate. I couldn't find sysdate in postgres documentation. What is the replacement for sysdate in PostgreSQL?
但是，PostgreSQL 似乎不支持 sysdate。我在 postgres 文档中找不到 sysdate。PostgreSQL 中 sysdate 的替代品是什么？
回答by a_horse_with_no_name
SYSDATEis an Oracle only function.
SYSDATE是 Oracle 唯一的函数。
The ANSI standard defines current_dateor current_timestampwhich issupported by Postgres and documented in the manual:
http://www.postgresql.org/docs/current/static/functions-datetime.html#FUNCTIONS-DATETIME-CURRENT
ANSI标准定义current_date或current_timestamp其中是通过Postgres的支撑，并且记录在手册中：
http://www.postgresql.org/docs/current/static/functions-datetime.html#FUNCTIONS-DATETIME-CURRENT
(Btw: Oracle supports CURRENT_TIMESTAMPas well)
（顺便说一句：Oracle 也支持CURRENT_TIMESTAMP）
You should pay attention to the difference between current_timestamp, statement_timestamp()and clock_timestamp()(which is explained in the manual, see the above link)
您应该注意current_timestamp,statement_timestamp()和之间的区别clock_timestamp()（手册中有解释，请参阅上面的链接）
This statement:
这个说法：
select up_time from exam where up_time like sysdate
select up_time from exam where up_time like sysdate
Does not make anysense at all. Neither in Oracle nor in Postgres. If you want to get rows from "today", you need something like:
没有任何意义。无论是在 Oracle 中还是在 Postgres 中。如果你想从“今天”获取行，你需要这样的：
select up_time
from exam
where up_time = current_date
Note that in Oracle you would probably want trunc(up_time) = trunc(sysdate)to get rid of the time part that is always included in Oracle.
请注意，在 Oracle 中，您可能希望trunc(up_time) = trunc(sysdate)摆脱始终包含在 Oracle 中的时间部分。
回答by Virendra Patel
NOW()is the replacement of Oracle Sysdate in Postgres.
NOW()是 Postgres 中 Oracle Sysdate 的替代品。
Try "Select now()", it will give you the system timestamp.
尝试“ Select now()”，它会给你系统时间戳。
回答by segfault
You may want to use statement_timestamp(). This give the timestamp when the statement was executed. Whereas NOW()and CURRENT_TIMESTAMPgive the timestamp when the transaction started.
您可能想要使用statement_timestamp()。这给出了执行语句时的时间戳。而NOW()并CURRENT_TIMESTAMP给出交易开始时的时间戳。
More details in the manual
手册中的更多详细信息
回答by abhinav kumar
The following functions are available to obtain the current date and/or time in PostgreSQL:
以下函数可用于获取 PostgreSQL 中的当前日期和/或时间：
CURRENT_TIME
CURRENT_DATE
CURRENT_TIMESTAMP
Example
例子
SELECT CURRENT_TIME;
08:05:18.864750+05:30
SELECT CURRENT_DATE;
2020-05-14
SELECT CURRENT_TIMESTAMP;
2020-05-14 08:04:51.290498+05:30
