How to get partial time in SQL

How to get partial time in sql:

Sometimes, we may want to do some data by month, by day, and by year, but the data we actually save may be a very precise occurrence, possibly to a second. How to intercept a part of a time is a problem.

There are two solutions:

The most direct idea is to use datepart or year, Month, day functions

CAST (

(

STR (Year (GETDATE ())) + '/' +

STR (MONTH (GETDATE ())) + '/' +

STR (Day (GETDATE ()))

)

As DATETIME

)

If it's only a year and a month, skip the front.

Method two, using the time calculation function

For example get month

DATEADD (month, DateDiff (month, 0, Coltime), 0)

The principle is the database time value Coltime minus 1900-1-1 to get the number of months of this period, and then add back to 1900-1-1.