Small question, how to get the number of days from a certain date in SQL?

流星飞舞

There is a birthday date A (2000-02-01), how do I get the number of days before this birthday date (February-01)?

psycholmu

For example, use the datediff function in SQL Server.

流星飞舞

This will not work.

苹果小刀

select datediff (day, '2017-01-03', getdate ())

shygza

SQL Server
select DATEDIFF (day, convert (datetime, '20170101', 112), getdate ())

Oracle
select to_date (to_char (sysdate, 'yyyy-mm-dd'), 'yyyy-mm-dd')-to_date ('2017-01-01', 'yyyy-mm-dd') from dual

psycholmu

SELECT DAY (BirthDate)-DAY (GETDATE ()) AS Expr1
FROM Employees

流星飞舞

thank you very much!

22151146

This question is not so simple.
For example, if the birthday is June 1.
If the current date is May 1, 2017, then it should be 30 days.
If the current date is June 2, 2017, then it should be 364 days. Instead of 1 day.

shygza

To process only the month, it is OK to add a string to the current year.
select DATEDIFF (day, convert (datetime, substring (convert (varchar, getdate (), 112), 1,4) + substring ('20000101', 5, len ('20000101')), 112), getdate ())

hundan3

Then convert it to a string? Substring is only available for strings