SQL獲取兩個日期之間的天數

DATEDIFF()函數返回兩個日期之間的時間
DATEDIFF(datepart,startdate,enddate)

-- 獲取兩個日期之間的天數
SELECT DATEDIFF(day,'2021-01-01','2021-06-10') AS days;
SELECT DATEDIFF(day,'2021-01-01 08:00:00','2021-06-10 09:00:00') AS days;

-- 獲取兩個日期之間的月數
SELECT DATEDIFF(month,'2021-01-01','2021-06-10') AS months;
SELECT DATEDIFF(month,'2021-01-01 08:00:00','2021-06-10 09:00:00') AS months;

-- 獲取兩個日期之間的年數
SELECT DATEDIFF(year,'2021-01-01','2022-06-10') AS years;
SELECT DATEDIFF(year,'2021-01-01 08:00:00','2022-06-10 09:00:00') AS years;

-- startdate位置0表示1900-01-01，-1表示1899-12-31
SELECT DATEDIFF(day, 0, '1900-01-01');-- 結果：0
SELECT DATEDIFF(day, 0, '1900-01-31');-- 結果：30
SELECT DATEDIFF(day, -1, '1900-01-01');-- 結果：1
SELECT DATEDIFF(day, -1, '1900-01-31');-- 結果：31