NOW（）和DATE（NOW（））之间有什么区别？

What is the difference between NOW() and DATE(NOW()) in terms of performance, results and precision? How will MySQL understand those 2 functions?

NOW()和DATE(NOW())在性能,结果和精度方面有什么区别? MySQL将如何理解这两个功能?

I was wondering what is the best between

我想知道什么是最好的

 WHERE the_date < NOW()

and

WHERE the_date < DATE(NOW())

3 个解决方案

#1

NOW() returns current date/time. DATE(NOW()) returns the date part. If you want to know only the date, use CURRDATE().

NOW()返回当前日期/时间。 DATE(NOW())返回日期部分。如果您只想知道日期,请使用CURRDATE()。

#2

You are looking at two different comparisons.

您正在寻找两种不同的比较。

Since the_date contains a time of day, the expression the_date < NOW() will take into account the time of day at the moment you execute the SQL statement, which could make a difference if the YYYY-MM-DD in the_date is the same as the current datetime.

由于the_date包含一天中的某个时间,因此表达式the_date ()将考虑执行sql语句时的一天中的时间,如果the_date中的yyyy-mm-dd与之相同,则可能会有所不同。当前的日期时间。

In the case of the_date < DATE(NOW()), you are comparing the_date to YYYY-MM-DD 00:00:00000, so the current time of day from NOW() is ignored and set to midnight.

在the_date (now())的情况下,您将the_date与yyyy-mm-dd>

What is more important here is what you need to do and what results you are expecting.

这里更重要的是你需要做什么以及你期望得到什么结果。

#3

The DateTime.Now property returns the current date and time, for example 2011-07-01 10:09.45310.

DateTime.Now属性返回当前日期和时间,例如2011-07-01 10:09.45310。

The DateTime.Today property returns the current date with the time components set to zero, for example 2011-07-01 00:00.00000.

DateTime.Today属性返回时间组件设置为零的当前日期,例如2011-07-01 00:00.00000。

The DateTime.Today property actually returns DateTime.Now.Date:

DateTime.Today属性实际上返回DateTime.Now.Date:

#1