SQL Server 计算时间差DATEDIFF 函数

SELECT datediff( hour, '4:00AM', '5:50AM' ) --返回 1

SELECT datediff( month, '1987/05/02', '1995/11/15' ) --返回 102

SELECT datediff( day, '00:00', '23:59' )   --返回 0

SELECT datediff( day,'1999/07/19 00:00','1999/07/23 23:59' )   --返回 4

SELECT datediff( month, '1999/07/19', '1999/07/23' )   --返回 0

SELECT datediff( month, '1999/07/19', '1999/08/23' )  --返回 1