SQL datediff calculation time difference

For information about datediff, see:

DATEDIFF (datepart ,startdate ,enddate )

Datepart

Is part of startdate and enddate of the specified cross-border type. The following table lists all valid datepart parameters. The user-defined equivalent variable is invalid.

Datepart	Abbreviations
Year	YY, yyyy
Quarter	QQ, Q
Month	Mm, m
Dayofyear	Dy, y
Day	DD, d
Week	Wk, WW
Hour	HH
Minute	Mi, n
Second	SS, S
Millisecond	MS
Microsecond	MCS
Nanosecond	NS

Startdate

Is an expression that can be parsed to time, date, smalldatetime, datetime, datetime2, or datetimeoffset values. Date can be an expression, column expression, user-defined variable, or string text. Subtract startdate from enddate.

To avoid uncertainty, use a four-digit year. For information about the two-digit year, see the two digit year cutoff option.

Enddate

See startdate.

1. Return two-quarter time difference records

The Code is as follows: if necessary, you can change the time field to the corresponding field in the database.

View code

1 declare @ startdatetime
2 declare @ enddatetime
3 set @ startdatetime = '2017-01-01'
4 set @ enddatetime = '2017-07-10'
5 select datediff (QQ, @ startdatetime, @ enddatetime)

2. Search for orders in the last three months.

The Code is as follows:

View code

Declare @ startdatetime
Declare @ enddatetime
Set @ startdatetime = '2017-05-01'
Set @ enddatetime = getdate ()
Select datediff (M, @ startdatetime, @ enddatetime)

3. Return the number of days between the time of the first order and the time of the last order.

Select datediff (day, (select Min (insdt) from op_order), (select max (insdt) from op_order ))

4. Use the getdate () function to obtain the current time,

If getdate () + 1 is used, the result is to add one more day in the current time.

For example:

Getdate (): 2011-08-13 13:53:09. 243

Getdate () + 1: 2011-08-14 13:53:09. 243

As shown above, add 1 directly in the period of time.