计算给定日期和current_timestamp之间的天数

Question

我正在尝试获取帐户到期之前的剩余天数,因此我可以向用户发送电子邮件通知他们.我有正确的"Where"语句,但我不确定如何选择差异作为整数.到目前为止,我有:

SELECT (DATE_EXPIRE-CURRENT_TIMESTAMP),EMAIL 
FROM [myTable] 
WHERE (DATE_EXPIRE - CURRENT_TIMESTAMP <= 10) AND (DATE_EXPIRE - CURRENT_TIMESTAMP >= 1)

Answer 1

SELECT DATEDIFF(DAY, CURRENT_TIMESTAMP, DATE_EXPIRE),EMAIL 
FROM dbo.[myTable] 
WHERE DATEDIFF(DAY, CURRENT_TIMESTAMP, DATE_EXPIRE) BETWEEN 1 AND 10;

我实际上提倡使用BETWEEN的少数情况之一.虽然我还是喜欢设置明确的界限:

DECLARE @tomorrow DATE = DATEADD(DAY, 1, CURRENT_TIMESTAMP);

SELECT DATEDIFF(DAY, CURRENT_TIMESTAMP, DATE_EXPIRE),EMAIL 
FROM dbo.[myTable] 
WHERE DATE_EXPIRE >= @tomorrow
AND DATE_EXPIRE < DATEADD(DAY, 10, @tomorrow);

您不应该使用速记数学(例如datetime - integer),因为虽然它适用于DATETIME/SMALLDATETIME,但如果您将数据类型更改为DATE,DATETIME2等,它会中断.

对于日期范围查询中的许多我的ramblings:

• 糟糕的习惯:错误处理日期/范围查询