how to find difference between two dates in sql code example

Example 1: date difference in number of days sql server

DECLARE 
    @start_dt DATETIME2= '2019-12-31 23:59:59.9999999', 
    @end_dt DATETIME2= '2020-01-01 00:00:00.0000000';

SELECT 
    DATEDIFF(year, @start_dt, @end_dt) diff_in_year, 
    DATEDIFF(quarter, @start_dt, @end_dt) diff_in_quarter, 
    DATEDIFF(month, @start_dt, @end_dt) diff_in_month, 
    DATEDIFF(dayofyear, @start_dt, @end_dt) diff_in_dayofyear, 
    DATEDIFF(day, @start_dt, @end_dt) diff_in_day, 
    DATEDIFF(week, @start_dt, @end_dt) diff_in_week, 
    DATEDIFF(hour, @start_dt, @end_dt) diff_in_hour, 
    DATEDIFF(minute, @start_dt, @end_dt) diff_in_minute, 
    DATEDIFF(second, @start_dt, @end_dt) diff_in_second, 
    DATEDIFF(millisecond, @start_dt, @end_dt) diff_in_millisecond;

Example 2: find difference in dates sql

SELECT DATEDIFF(day, date1,date2) AS DateDiff
/*
DATEDIFF accepts three arguments
1- day, month, year etc what form you need difference
2,3- dates 
*/

Example 3: sql get number of days between two dates

DATEDIFF(DAY, '1/1/2011', '3/1/2011')

Example 4: difference in dates sql

SELECT (END_DATE - START_DATE) Days-Total FROM MyTable
/*this works for oracle sql*/

Example 5: how to get the date diff of 2 dates in the same fieldin sql server

WITH Partitioned AS(	SELECT *, ROW_NUMBER() OVER (PARTITION BY cu_id, date ORDER BY cu_id, date) AS RowNumber	FROM @Table) SELECT 	*,	CASE 		WHEN RowNumber > 1 THEN 0		ELSE COALESCE(DATEDIFF(DAY, (SELECT MAX(date) FROM @Table WHERE date < a.date AND cu_id = a.cu_id), a.date), 0)	END AS Days_betweenFROM Partitioned a