What is the function of the dateadd function in SQL Ser…

1 year ago
Sophia Anderson
2 minutes

The DATEADD function in SQL Server is used to add or subtract a specified time interval to a given date. It functions by increasing or decreasing a specified date by a certain amount based on a specified unit (such as year, month, day, hour, minute, etc.).

The syntax of the DATEADD function is as follows:

DATEADD (datepart, number, date)

The datepart parameter specifies the unit of time to add or subtract, and can be one of the following values:

  1. year
  2. quarter: a period of three months
  3. month: a unit of time that is approximately four weeks long, usually containing 30 or 31 days.
  4. Number of days in a year
  5. day: sun
  6. week: seven days
  7. Number of days within a week.
  8. hour: a unit of time equal to 60 minutes
  9. minute: a unit of time equal to 60 seconds
  10. second: a unit of time equal to 1/60th of a minute
  11. millisecond: a unit of time equal to one thousandth of a second
  12. microsecond means a very short period of time
  13. nanosecond: a unit of time equal to one billionth of a second

The number parameter specifies the quantity to be added or subtracted, which can be positive (towards the future) or negative (towards the past).

The date parameter is a date or time value that represents the reference date for the operation.

The DATEADD function returns a new date value that is the result of adding or subtracting a specified time interval to a given date.

Here are some examples of using the DATEADD function:

-- 在当前日期上增加一个月
SELECT DATEADD(month, 1, GETDATE())

-- 在指定日期上减去一个小时
SELECT DATEADD(hour, -1, '2022-01-01 10:30:00')

-- 在指定日期上增加两周
SELECT DATEADD(week, 2, '2022-01-01')

-- 在指定日期上增加 30 分钟
SELECT DATEADD(minute, 30, '2022-01-01 10:00:00')

Using the DATEADD function makes it easy to perform calculations and manipulate dates and times.

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